Wireless communication terminal

ABSTRACT

According to one embodiment, a wireless communication terminal including a receiver, a first processor, a first storage, a second storage, a second processor, and a transmitter is provided. The receiver receives one physical packet that includes at least one frame body field, a first field including information on a length of the frame body field, a second field used to detect an error of the frame body field, and a sequence number field including a sequence number corresponding to the frame body field. The second storage retains a successively and successfully received maximum sequence number on the basis of a result of the first processor. The transmitter transmits a response frame indicating the successively and successfully received maximum sequence number when the first processor extracts at least one correct frame body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional of U.S. application Ser. No. 13/223,688, filed Sep.1, 2011, which is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2011-023216, filed Feb. 4, 2011,the entire contents of both of which are incorporated herein byreference.

FIELD

Embodiments described herein relate generally to a wirelesscommunication terminal that performs frame exchange using anacknowledgement.

BACKGROUND

For example, there is a method in which a sequence starting number and afixed-length bitmap are used as a method for indicating theacknowledgement to plural data frames by one response frame. Eachacknowledgement to the data frame of a relative sequence number from thesequence starting number is displayed in the fixed-length bitmap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a data frame format according to a first embodiment;

FIG. 2 shows an acknowledgement frame format of the first embodiment;

FIG. 3 shows a configuration of a wireless communication terminal of thefirst embodiment;

FIG. 4 shows a concrete receiving state of a data frame of the firstembodiment;

FIG. 5 shows another concrete receiving state of a data frame of thefirst embodiment;

FIG. 6 shows still another concrete receiving state of a data frame ofthe first embodiment;

FIG. 7 shows still another concrete receiving state of a data frame ofthe first embodiment;

FIG. 8 shows the detailed data frame format of the first embodiment;

FIG. 9 explains a method for extracting a frame body field and an FCSfield of the first embodiment;

FIG. 10 explains process of searching an SH field of the firstembodiment;

FIG. 11 shows an acknowledgement frame format according to a secondembodiment;

FIG. 12 shows a concrete exchange of a data frame and an acknowledgementframe of the second embodiment;

FIG. 13 shows another concrete exchange of a data frame and anacknowledgement frame of the second embodiment;

FIG. 14 shows still another concrete exchange of a data frame and anacknowledgement frame of the second embodiment;

FIG. 15 explains processing within a received data frame according to athird embodiment;

FIG. 16 explains another processing within the received data frame ofthe third embodiment;

FIG. 17 explains still another processing within the received data frameof the third embodiment;

FIG. 18 shows states of a receiving buffer and an SMSN retention unitaccording to a fifth embodiment;

FIG. 19 shows an example of a relationship among states of a receivingbuffer and an SMSN retention unit, reception of a data frame, andtransmission of an acknowledgement frame according to a seventhembodiment;

FIG. 20 shows another example of a relationship among the states of thereceiving buffer and the SMSN retention unit, the reception of a dataframe, and the transmission of an acknowledgement frame of the seventhembodiment;

FIG. 21 shows an example of a relationship among states of a receivingbuffer and an SMSN retention unit, reception of a data frame, andtransmission of an acknowledgement frame according to a ninthembodiment;

FIG. 22 shows another example of a relationship among the states of thereceiving buffer and the SMSN retention unit, the reception of a dataframe, and the transmission of an acknowledgement frame of the ninthembodiment;

FIG. 23 shows still another example of a relationship among the statesof the receiving buffer and the SMSN retention unit, the reception of adata frame, and the transmission of an acknowledgement frame of theninth embodiment;

FIG. 24 shows an example of a concrete exchange of a data frame and anacknowledgement frame according to a twelfth embodiment; and

FIG. 25 shows an example of an algorithm for determining whether anindication bit used to indicate start of a sequence number is correctlyused according to the twelfth embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a wireless communicationterminal including a receiver, a first processor, a first storage, asecond storage, a second processor, and a transmitter is provided. Thereceiver receives one physical packet that includes at least one framebody field, a first field including information on a length of the framebody field, a second field used to detect an error of the frame bodyfield, and a sequence number field including a sequence numbercorresponding to the frame body field. The first processor extracts thecorrect frame body field(s) using the first field(s) and the secondfield(s). The first storage retains the frame body field(s) extracted bythe first processor and the sequence number field(s) corresponding tothe frame body field(s). The second storage retains a successively andsuccessfully received maximum sequence number on the basis of a resultof the first processor. The second processor transfers the frame bodyfields corresponding to the sequence numbers up to the successively andsuccessfully received maximum sequence number from the first storage tocontinued receiving process. The transmitter transmits a response frameindicating the successively and successfully received maximum sequencenumber when the first processor extracts at least one correct framebody.

Hereinafter, embodiments will be described with reference to thedrawings.

A communication state of an electromagnetic wave having a millimeterwaveband at wavelengths of the order of millimeters, for example, a60-GHz band can be considered to be roughly divided into two cases,i.e., one case it is significantly good and in the other case it issignificantly bad (IEEE 802.11 doc.: IEEE 802.11-09/0302r0). Thefollowing embodiments relate to improvement of communication efficiencymainly in an operation of frame reception where such communication stateis expected.

First Embodiment

A frame used in wireless communication and a basic configuration of awireless communication terminal will be described.

In a first embodiment, the wireless communication terminal is connectedto another wireless communication terminal and uses three kinds offrames in conducting communication. A management frame is used to managea physical communication link with another wireless communicationterminal. Examples of the management frame include a frame used to startcommunication with another wireless communication terminal, a framereleasing the communication link (that is, terminating connection), anda frame relating to a power saving operation at the wirelesscommunication terminal.

A data frame transmits data generated in the wireless communicationterminal to another wireless communication terminal after the physicalcommunication link with another wireless communication terminal isestablished. The data are generated by an upper layer of the firstembodiment. For example, the data are generated by user operation.

A control frame is used to perform control when the data frame istransmitted to and received from (exchanged with) another wirelesscommunication terminal. One of the control frames is a response framethat is transmitted to acknowledge transmission when the wirelesscommunication terminal receives the data frame.

The three kinds of the frames are subjected to necessary processing in aphysical layer (hereinafter referred to as a PHY layer) and transmittedas a physical packet through an antenna.

FIG. 1 illustrates a format of the data frame of the first embodiment.An aggregation frame, in which the plurality of data items areaggregated into one physical packet, is dealt with in the firstembodiment. In FIG. 1, n data items are aggregated as a frame body. Forthe sake of convenience, a set of a subheader field (hereinafterreferred to as an SH field) 2, a frame body field (hereinafter referredto as an FB field) 3, and a frame check sequence field (hereinafterreferred to as an FCS field) 4 is collectively referred to as a-“frame”and expressed as frame #1, frame #2, . . . , frame #n.

Items of information, such as a transmitter unique ID (hereinafterreferred to as Tx UID) of the wireless communication terminal thattransmits the frame and a receiver unique ID (hereinafter referred to asRx UID) of the wireless communication terminal that receives the frame,which are common to the whole of the frame are set in a common headerfield (hereinafter referred to as a CH field) 5. The wirelesscommunication terminal that receives the frame judges whether the frameis addressed to it using the Rx UID. Then the receiving process isperformed according to the judgment. Therefore, preferably the Rx UID islocated at the head of the CH field 5 followed by the Tx UID.Information on the number of FB fields 3 aggregated thereafter may beset in the CH field 5. An error detecting field, namely, a header checksequence field (hereinafter referred to as HCS field) 6 may be added tothe CH field 5 to check whether the information in the CH field 5 iscorrectly received.

At least one data item is set after the CH field 5. Each data item isset in the FB field 3, and the SH field 2 and the FCS field 4 areassociated with the FB field 3.

A length field 7 indicating an FB field length, a sequence number field(hereinafter referred to as an SN field) 8 indicating the sequencenumber, and the HCS field 6 are set in the SH field. Although the HCSfield 6 is illustrated adjacent to the SH field 2 in FIG. 1, the HCSfield 6 is included in the SH field 2. The SH field 2 may includeinformation 9 indicating a frame type corresponding to the SH field andthe FB field. Because the frame is the data frame, the frame typeindicates that it is the data frame. For example, the information 9indicating the frame type may be expressed by one field or a pluralityof fields, for example, a first field discriminating the control framefrom the data frame/management frame and a second field discriminatingthe data frame from the management frame. It is sufficient if theinformation on the frame type can finally be discriminated at a level ofat least the data frame, the management frame, and the control frame.The information 9 indicating the frame type may be set in the CH header5 instead. The HCS field 6 is the error detecting field used to judgewhether the information in the SH field 2 is correctly received. Whetherthe data items in the SH field, such as the FB field length 7 and thesequence number 8, which are indicated by the SH field 2 can becorrectly extracted can be determined by providing the HCS field 6 inthe SH field 2.

The FCS field 4 subsequent to the FB field 3 is the error detectingfield used to judge whether the information in the FB field 3 iscorrectly received.

FIG. 2 illustrates a format of an acknowledgement frame transmitted bythe wireless communication terminal that receives the data frame in thefirst embodiment.

The CH header is similar to that in the data frame format. When there isa field which indicates the number of FB fields aggregated, the numberis set to 0 (zero) for the acknowledgement frame.

Although the SH field of FIG. 2 has the same configuration as the SHfield of FIG. 1, the SH field of FIG. 2 may have the configurationdifferent from that of the SH field of FIG. 1. However, at least the SNfield 2 indicating the sequence number and the HCS field 6 are set inthe SH field. Although the HCS field 6 is illustrated adjacent to the SHfield 2 in FIG. 2, as in FIG. 1, the HCS field 6 is included in the SHfield 2. When the information 9 indicating the frame type is set in theSH field similarly to the data frame, it indicates that this frame isthe control frame. The information 9 indicating the frame type may beset in the CH header 5 instead. As to a method for expressing theinformation 9 indicating the frame type, similarly to the data framewhose format is shown in FIG. 1, the information 9 may be expressed byone field or the plurality of fields, for example, the first fielddiscriminating the control frame from the data frame/management frameand the second field discriminating the data frame from the managementframe. The frame is the control frame, and the frame is independent ofthe second field discriminating the data frame from the management framewhen the frame type is expressed by the plurality of fields as describedabove. Therefore, the second field becomes reserved. When the SH field 2of the acknowledgement frame has the same configuration as the SH field2 of the data frame in FIG. 1, the length field may be set to reservedor, for example, 0 (zero) may be set because the FB field does notexist.

In the acknowledgement frame of the first embodiment, the SN field 2indicates the maximum sequence number among the frames that weresuccessively and successfully received by the wireless communicationterminal, i.e., the successive maximum sequence number (hereinafterreferred to as an SMSN) 8′.

The HCS field 6 that is the error detecting field is provided at the endof the SH field 2 of the acknowledgement frame to judge whether theinformation in the SH field 2 is correctly received.

By such format of an acknowledgement frame, the response frame lengthcan be shortened to improve the communication efficiency under thesignificantly good communication environment compared with the method ofthe related art which indicates acknowledgement to each of the pluralityof frame bodies, namely, each data item. Also, only one receiving statemay be retained as information input to the acknowledgement frame.

The frames including the data frame and the acknowledgement frame aresubjected to coding process in a physical layer, a physical header and apreamble are provided to the frames, and the frames are transmitted fromthe antenna after modulation.

FIG. 3 illustrates the configuration of the wireless communicationterminal of the first embodiment.

A reception processor 10 and a transmission processor 20 are connectedto an upper layer processor 0, an access controller 30, and a PHYprocessor 40. The PHY processor 40 includes a receiver that receives thephysical packet and a transmitter that transmits the physical packet,and the PHY processor 40 is connected to an antenna 60 through afrequency conversion circuit 50.

In the wireless communication terminal of the first embodiment, aconfiguration of a wireless communication device unit may include theantenna 60 of FIG. 3. By including the antenna 60 in the wirelesscommunication device unit, one can configure a wireless communicationdevice as one device including the antenna, so that a mounting area canbe suppressed. Also, in FIG. 3, the antenna 60 is shared by thetransmission processor 20 and the reception processor 10. When the oneantenna is shared by the transmission processor and the receptionprocessor, the wireless communication device can be miniaturized.

The transmitter of the PHY processor 40 performs processing such ascoding to the frame received from the transmission processor 20 andconverts the frame into a physical packet. The physical packet ismodulated into a radio signal having a necessary frequency band, forexample, a 60-GHz millimeter waveband by the frequency conversioncircuit 50 and radiated from the antenna 60. Although the antenna 60 isshown to be consisting of plurality of antennas in FIG. 3, it may be asingle antenna.

In receiving a radio signal, the frequency conversion circuit 50demodulates the radio signal received from the antenna 60 into a baseband signal that can be processed by the PHY processor 40, and thefrequency conversion circuit 50 transfers the demodulated radio signalto the receiver of the PHY processor 40. After the receiver performsphysical packet decoding process and process of removing the preambleand the physical header, a payload portion is transferred as the framefrom the PHY processor 40 to the reception processor 10. Before theframe transferred to the reception processor 10, an indication ofstarting to receive the physical packet is input to the receptionprocessor 10. After the frame is transferred to the reception processor10, an indication of ending the reception is input to the receptionprocessor 10. An indication of detecting the error of the physicalpacket and information on a state of a wireless medium are input to theaccess controller 30.

The reception processor 10, the transmission processor 20, and theaccess controller 30 deal with the data frame, the control frame, andthe management frame and establish a wireless link with another wirelesscommunication terminal to exchange the frames. The reception processor10, the transmission processor 20, and the access controller 30 performprocessing relating to at least media access control (hereinafterreferred to as MAC). As to the data frame, the reception processor 10,the transmission processor 20, and the access controller 30 performprocess including process to sort the data items on the reception sidesuch that the order of the data reception matches the order of the datatransmission at a level of an application layer between the wirelesscommunication terminals that exchange the data.

The plurality of different PHY processors and the transmissionprocessor, the reception processor, and the access controller, whichcorrespond to each of the PHY processors, may be provided, and a commonprocessor across the different PHY processors may be further provided.

When transmission data are generated by user operation in theapplication layer for example, the data are transferred to thetransmission processor 20 through the upper layer processor 0 andconverted into data frames whose format is shown in FIG. 1 by thetransmission processor 20. Each data item is handled as a frame body andis set in a single FB field, or is fragmented into smaller units and isset across multiple FB fields. An integral counter that increments avalue by one is prepared in the transmission processor 20, and the valueof the counter is allocated as the sequence number to the SN fieldcorresponding to the frame body while the same type of the frame (inthis case, data frame) is transmitted to the same wireless communicationterminal. The transmission processor 20 measures transmission timing onthe basis of the information from the access controller 30, andtransfers the generated frame to the PHY processor 40 along with atransmission instruction. At this point, instructions of a modulationscheme and a coding scheme necessary to the transmission maysimultaneously be issued.

In the wireless communication terminal that receives the data framethrough the PHY processor 40, the reception processor 10 generates anacknowledgement frame whose format is shown FIG. 2 in response to thedata frame and transmits the acknowledgement frame as the physicalpacket after waiting a predetermined interframe space (hereinafterreferred to as IFS) from the end of the physical packet including thedata frame. The reception processor 10 also sequentially transferscontents of the FB field in the received data frame to the upper layerprocessor 0 on the basis of the SN field.

In the first embodiment, when at least one FB field is correctlyextracted from the received data frame, the acknowledgement frame inwhich the maximum sequence number among the frames that weresuccessively and successfully received, i.e., SMSN, is set in the SNfield is transmitted after the IFS of the data frame reception. When theSMSN is updated by the frame body that is newly correctly extracted fromthe received frame, the frame body is transferred to the upper layerprocessor 0. For this purpose, the reception processor 10 includes adeaggregation/filter unit 12, a receiving buffer 14, a successivemaximum sequence number (SMSN) retention unit 16, and a receptioncoordinator 18. The reception processor 10 is not limited to theconfiguration shown in FIG. 3, but any configuration may be adopted aslong as the purpose can finally be accomplished.

The deaggregation/filter unit 12 performs deaggregation process toseparate and extract each FB field when the FB fields are aggregated,and the deaggregation/filter unit 12 also performs filtering process tofilter only the frames necessary for the subsequent receiving process.

When the frame type information is in the CH field, preferably theprocess is performed as follows. When the information on the number offrame bodies is described in the CH field and when it is zero, whetherthe frame type permits the number of frame bodies to be zero isconfirmed. Also, whether identifiers of the frame fall within apermissible range of Tx UID and a permissible range of Rx UID areconfirmed as a condition in processing the frame type. When thecondition is satisfied, the control frame is transferred to thereception coordinator 18, and the data frame is transferred to thereceiving buffer 14. When the management frame is managed by thesequence number, the management frame is transferred to the receivingbuffer 14 similarly to the data frame, and the transmission of theacknowledgement frame that is a response operation described later willbe also similar to that of the data frame. When the information on thenumber of frame bodies is 1 or more, the frame type is confirmed, andwhether the frame type permits the number of frame bodies is confirmed.Whether identifiers of the frame fall within the permissible range of TxUID and the permissible range of Rx UID are confirmed as the conditionin processing the frame type. The deaggregation process is performedwhen the condition is satisfied. When the received frame is out of thecondition in the filtering process, the frame is subjected to errorprocess or directly discarded according to the way the frame is out ofthe condition. Following the above procedure, the received frame issubjected to the deaggregation process in the case of the data frameaddressed to the wireless communication terminal, and the received frameis transferred to the reception coordinator 18 in the case of theacknowledgement frame addressed to the wireless communication terminal.In the deaggregation process, the aggregated FB fields are individuallyextracted by the information in the length field of the SH field.Whether the information in the SH field has no error is determined onthe basis of the HCS field set in the end of the SH field. When theinformation in the SH field is determined to have no error, namely,determined to be correct, the FB field is extracted using theinformation on the length field. Whether the information in each FBfield has no error is determined on the basis of the FCS fieldsubsequent to the FB field. The information in the FB field that isdetermined to have no error, namely, that is determined to be correct istransferred to the receiving buffer 14 along with the information on thecorresponding SN field (sequence number). The items of information onthe frame body, which are of the frame body length (length field) andthe sequence number (SN field), are concentrated in one place, wherebythe information used in the deaggregation/filter unit 12 and thereceiving buffer 14 is easily extracted. When the information in the FBfield is correctly extracted and that is the first one after start ofthe reception frame process, an instruction to start preparation of theacknowledgement frame is transferred to the reception coordinator 18.When at least one FB field is correctly extracted from the receivedframe by this indication to the reception coordinator 18, the receptioncoordinator 18 prepares the transmission of the acknowledgement frame inresponse to the instruction. After the extraction and the determinationare made to the FB field to which the SH field is associated and the FCSfield subsequent to the FB field, the SH field next to the FCS field issearched to continue the similar operation. When the process iscompleted up to the end of the received frame, an indication of endingthe reception frame process is transferred to the reception coordinator18. At this point, an actual time in which the reception frame processis ended is added to the indication. A time at which the indication ofthe end of the reception frame is received from the PHY processor 40 isrecognized, and a processing delay generated until the recognition ofthe indication is subtracted from the time at which the indication ofthe end of the reception frame is received, thereby fixing the time atwhich the received frame is ended. When the number of actually extractedframe bodies differs from the information on the number of frame bodies,the received frame is subjected to the error process. The deaggregationprocess may be ended at a stage at which the number of extracted framebodies becomes equal to the information on the number of frame bodies.

When the frame type information is set in the SH field, in the case ofthe frame addressed to the wireless communication terminal, thenecessary information depending on the frame type is appropriatelytransferred to the reception coordinator 18 and the receiving buffer 14while the deaggregation process by the SH field(s) is performed. Whenthe information on the number of frame bodies is zero, whether the frametype permits the number of frame bodies of zero is confirmed using thenext SH field. When the identifiers of the frame fall within thepermissible range of Tx UID and the permissible range of Rx UID as thecondition in processing the frame type, the frame is transferred to thereception coordinator 18. When the information on the number of framebodies is 1 or more, whether the frame type permits the number of framebodies is confirmed using the initial SH field immediately after the CHfield. Whether the identifiers of the frame fall within the permissiblerange of Tx UID and the permissible range of Rx UID is confirmed as thecondition in processing the frame type. The deaggregation process isperformed when the condition is satisfied.

The deaggregation process is similarly performed. However, during thedeaggregation process, the frame type information described in each SHfield is confirmed to determine the permissible frame type and when theframe is out of the condition, the frame is subjected to the errorprocess. For example, it is assumed that only the frame bodies of asingle frame type can be aggregated in one frame. In such case, when aframe in which the frame bodies having different frame types are mixed,for example a frame with the initial SH field indicating the data frameand the next SH field indicating the management frame is received, theframe is subjected to the error process.

The information (frame body) in the FB field determined to be correctand the corresponding sequence number are retained in the receivingbuffer 14 while paired with each other. Preferably the pairs of theframe bodies and the sequence numbers are reordered in the order of thesequence numbers. The receiving buffer 14 refers to the maximum sequencenumber retained by the SMSN retention unit 16. When there is a sequencenumber that is larger than the maximum sequence number by 1, the framebody corresponding to the sequence number larger than the maximumsequence number by 1 is transferred to the reception coordinator 18, andthe SMSN retention unit 16 is notified of the sequence number largerthan the maximum sequence number by 1. Preferably an area in which theframe body and the sequence number corresponding to the frame body areretained is cleared when the receiving buffer 14 transfers the framebody to the reception coordinator 18.

The SMSN retention unit 16 retains the sequence number of which thereceiving buffer 14 notifies the SMSN retention unit. Therefore, theSMSN retention unit 16 retains the SMSN that is successfully received.

The reception coordinator 18 works with the transmission processor 20 orthe upper layer processor 0 in response to the input from thedeaggregation/filter unit 12. When receiving the indication of the startof the preparation of the acknowledgement frame, the receptioncoordinator 18 waits for the indication of the end of the receptionframe process. When receiving the indication of the end of the receptionframe process, the reception coordinator 18 obtains the SMSN from theSMSN retention unit 16 and issues an instruction to transmit theacknowledgement frame including the SMSN and the time at which thereceived frame ended to the transmission processor 20. When the errorprocess is invoked due to the reception of the improper frame before theindication of the end of the reception frame process is received sincethe indication of the start of the preparation of the acknowledgementframe is received, preferably the start of the preparation of theacknowledgement frame is suspended. When the FB field is input to thereception coordinator 18 from the receiving buffer 14, the receptioncoordinator 18 transfers the FB field, namely, the frame body, to theupper layer processor 0. When the acknowledgement frame is input to thereception coordinator 18, the reception coordinator 18 transfers theinformation on the acknowledgement described in the frame to thetransmission processor 20. In the first embodiment, because thenotification of the successfully received SMSN is made by theacknowledgement frame, the transmission processor 20 is notified of theSMSN. Preferably the transmission processor 20 is simultaneouslynotified of the Tx UID of the acknowledgement frame, namely, theidentifier of the wireless communication terminal that transmitted theacknowledgement frame.

When receiving the instruction to transmit the acknowledgement frame,the transmission processor 20 generates the acknowledgement frame whoseformat is shown in FIG. 2 in which the SMSN is set in the SN field, andtransfers the acknowledgement frame to the PHY processor 40 such thatthe acknowledgement frame is transmitted after a fixed time elapsessince the indicated time at which the received frame ended. The fixedtime preferably is the defined minimum IFS and is the total of the timerequired when switching between transmission and reception and theprocessing delay cost to recognize that the reception frame requiresacknowledgement and generate and transmit the acknowledgement frame.Generally the minimum IFS is called a short interframe space(hereinafter referred to as an SIFS). When the information on theacknowledgement is received from the reception coordinator 18, processto retransmit appropriate frames is performed using the information. Inthe first embodiment, when the indication of the SMSN is received, theframe bodies whose sequence numbers are larger than the indicatedsequence number are retransmitted. The sequence of generating andtransmitting the data frame including the retransmitted frame bodies issimilar to the sequence described above. By simultaneously receiving theTx UID of the acknowledgement frame and the SMSN, the determination thatthe retransmission process should be performed to the frame bodieshaving the Rx UID same with the Tx UID can be made. That is, when theacknowledgement frame is received from the wireless communicationterminal to which the data frame is transmitted, the retransmission canproperly be performed to the wireless communication terminal. Theprocess of retransmitting all the frame bodies included in the framewhen an acknowledgement frame is not received within a predeterminedtime after the transmission of the frame (data frame or managementframe) which is the subject of retransmission process is similar to thewell-known technique.

The sequence numbers are used to make the data sequences of the wirelesscommunication terminal on the data transmission side and the wirelesscommunication terminal on the data reception side identical as commonrecognition. In the first embodiment, on the basis of the information inthe SN field, the received frame body information can be passed to theupper layer through the reception coordinator 18 by the above operationof the receiving buffer 14 while correlated with the sequence in thewireless communication terminal on the data transmission side. The framebody information may directly be transferred from the receiving buffer14 to the upper layer processor 0 without reordering.

When receiving the frame body information of the received frame from thereception processor 10, the upper layer processor 0 performs continuedreceiving process such that the frame body is input as the data to theapplication. The frame body information is transferred from thereception processor 10 to the continued receiving process.

Therefore, frame exchange for data on the basis of the acknowledgementcan be accomplished between the wireless communication terminals.

The case of receiving data frame shown as FIG. 4 will specifically bestudied hereinafter. It is assumed that the CH field is correctlyreceived. That is, it is assumed that the CH field includes the HCSfield, and it is assumed that the error is not detected by the HCSfield. When the CH field is not correctly received, the acknowledgementframe is not transmitted. The HCS field in each SH field and the FCSfield associated with each FB field are omitted. However, a mark “◯” isindicated below the SH field or the FB field when the SH field or the FBfield is determined to be not erroneous by the HCS field or the FCSfield (that is, the SH field or the FB field is correct), and a mark “x”is indicated below the SH field or the FB field when the error isdetected by the HCS field or the FCS field. For the sake of convenience,the SH field and the FB field of the first frame set are expressed bySH1 and FB1, the SH field and the FB field of the second frame set areexpressed by SH2 and FB2, the SH field and the FB field of the thirdframe set are expressed by SH3 and FB3, and the SH field and the FBfield of the fourth frame set are expressed by SH4 and FB4. In FIG. 4,the data frame includes four frame sets, where the SH fields and the FBfields of the first, second, and third frame sets are correctlyreceived, but for the fourth frame set, the error is detected in the SHfield and therefore the FB field is determined to be erroneous (when SH4is determined to be erroneous by the corresponding HCS field, theoperation to determine FB4 using the corresponding FCS field may beomitted). When the sequence numbers 101, 102, 103, and 104 are allocatedto the SN fields of SH1, SH2, SH3, and SH4, respectively, because themaximum sequence number that is successively and successfully receivedin the wireless communication terminal is 103, the acknowledgement framein which 103 is set in the SN field is transmitted to the wirelesscommunication terminal that transmitted the data frame. When receivingthe acknowledgement frame in which 103 is set in the SN field, thewireless communication terminal that transmitted the data framerecognizes it is necessary to retransmit the data corresponding to thesequence number 104, and the wireless communication terminal transmits adata frame including the frame set which was previously SH4 and FB4.

Again, a data frame having the same sequence numbers with the data frameof FIG. 4 is considered. For example, as illustrated in FIG. 5, when FB3is determined to be erroneous on the basis of the corresponding FCSfield while SH3 of the third frame set is determined to be correct onthe basis of the HCS field, the acknowledgement frame in which 102 isset in the SN field is transmitted to the wireless communicationterminal that transmitted the data frame. When receiving theacknowledgement frame in which 102 is set in the SN field, the wirelesscommunication terminal that transmitted the data frame recognizes it isnecessary to retransmit the data items from the sequence number 103, andthe wireless communication terminal retransmits the frame set of SH3 andFB3 and the frame set of SH4 and FB4. The frame set of SH3 and FB3 andthe frame set of SH4 and FB4 may be aggregated in one data frame, or theframe set of SH3 and FB3 and the frame set of SH4 and FB4 mayindividually be transmitted as a data frame in which the CH field isadded to the head of each of the frame sets. The data frame may beconfigured by also adding the frame sets that are not yet transmitted tothe retransmitted frame sets.

The case of a data frame whose reception status is shown as FIG. 6 willbe considered. When the sequence numbers are allocated the same with thedata frame of FIG. 4, the frame sets corresponding to the sequencenumbers 101, 102, and 103 are unsuccessfully received while only theframe set corresponding to the sequence number 104 is successfullyreceived. In the case of the receiving result of FIG. 6, the wirelesscommunication terminal generates and transmits the acknowledgement framebecause the fourth frame set can be correctly extracted, but the maximumsequence number that is successively and successfully received is notupdated by the reception of the data frame. If the data frames up to thesequence number 100 are successfully received before the reception ofthe data frame of FIG. 6, the sequence number 100 is retained as thesuccessively and successfully received maximum sequence number. In suchcase, the acknowledgement frame in which the sequence number 100 is setis transmitted in response to the data frame of FIG. 6. The wirelesscommunication terminal that transmitted the data frame recognizes it isnecessary to retransmit the data items from the sequence number 101. Andfurther by the fact that the acknowledgement is received from thewireless communication terminal of the destination, the wirelesscommunication terminal can recognize that some of the data itemssuccessfully reached the wireless communication terminal of thedestination, namely, the connection state is maintained, and that thewireless communication terminal of the destination is currently in areceivable state even if the wireless communication terminal of thedestination performs a power-saving operation. This serves as asubstitute for transmitting a probe frame to confirm the connection withthe other wireless communication terminal of the communication pair orconfirm whether the other wireless communication terminal of thecommunication pair is in a receivable state even if the other wirelesscommunication terminal performs a power-saving operation.

The case of a data frame whose reception status is shown as FIG. 7 willbe considered. When the sequence numbers are allocated the same with thedata frame of FIG. 4, the frame sets corresponding to the sequencenumbers 101, 102, and 103 are unsuccessfully received, and the error isdetected in FB4 of the frame set corresponding to the sequence number104. In the case of the receiving result of FIG. 7, because the wirelesscommunication terminal can not extract any correct frame body, namely,any data item, the wireless communication terminal does not generate andtransmit the acknowledgement frame. Because the wireless communicationterminal that transmitted the data frame does not receive theacknowledgement frame from the wireless communication terminal of thedestination after the fixed time elapses since the data frame istransmitted, the wireless communication terminal that transmitted thedata frame determines that the data did not reach the wirelesscommunication terminal of the destination, and retransmits the dataitems which were waiting for the acknowledgement frame and wereretransmission candidates, namely, the frame sets corresponding to thesequence numbers 101 to 104.

When not receiving the acknowledgement frame, the wireless communicationterminal on the data transmission side determines that the wirelesscommunication terminal of the destination fails to receive all the framesets in the transmitted data frame and performs the retransmittingprocess. When having a mechanism to transmit a frame (that is preferablythe control frame) requesting the acknowledgement frame, the wirelesscommunication terminal on the data transmission side may transmit therequest frame. The data-reception-side wireless communication terminalthat receives the request frame transmits an acknowledgement frame withthe value retained by the SMSN retention unit 16 set in theacknowledgement frame.

In the cases of FIGS. 6 and 7, because SH fields in the first half areerroneous, the FB fields and the FCS fields cannot be extracted, and itis unclear where the next SH field starts. Therefore, when the SH fieldis determined to be erroneous by the HCS field, an operation to searchthe next SH field is performed. The operation is performed by thedeaggregation/filter unit 12 of FIG. 3.

The SH field, the HCS field of the SH field, and the FCS field after theFB field are required to have fixed lengths. Preferably the length ofthe SH field is in a unit of bytes and a padding field (hereinafterreferred to as a PAD field) is appended after the FB field such that thesum of the lengths from the FB field to the FCS field becomes anintegral multiple of the length of the SH field. At this point, it isassumed that the SH field has the length of 8 bytes, and it is assumedthat the HCS field included in the SH field has the length of 4 bytes.It is also assumed that the FCS field has the length of 4 bytes. Thenthe PAD field becomes 0 to 7 bytes. Desirably each bit in the PAD fieldis set to 0. The format of such data frame is shown in FIG. 8. As thelength field in the SH field does not include the length of the PADfield, the wireless communication terminal on the data reception sidecan extract only the FB field using the value of the length field. Itcan be determined that the FCS field is located in an area of 4 bytesreturning from a point of the minimum integral multiple of the length of8 bytes of the SH field larger than the FB field counted up from thehead of the FB field. The operation will be described with reference toFIG. 9. For example, when the length field indicates 18, 18 bytes afterthe SH field are extracted as the FB field, a point that is 24 byte awayfrom the base point immediately after the SH field is set to an endingpoint of the FCS field because the minimum integral multiple of 8 noless than 18 is 24, and the area of 4 bytes returning from the endingpoint of the FCS field can be extracted as the FCS field. It is notedthat an FCS field targets error detection only on an FB field and thePAD field is not included in the target of the error detection.

In the case of the configuration including aggregated frame sets,assuming that only the same frame type is permitted, the configurationof the control frame, such as the acknowledgement frame, which has onlyup to the SH field and does not have the FB field, the subsequent PADfield, nor the FCS field as shown in FIG. 2, is not included. At leastthe minimum length of the frame body, the PAD field, and the FCS fieldhaving the length of 4 bytes are inevitably located subsequent to theHCS field determined to be erroneous, and followed by the next SH field.Because the sum of the minimum length of the frame body, the length ofthe PAD field, and the length of 4 bytes of the FCS field is theintegral multiple of the length of an SH field, the search startingpoint of the next SH field may be shifted by the integral multiple ofthe length of the SH field from a base point immediately after thecurrent SH field. This will be described with reference to FIG. 10. Forexample, when 0 byte is permitted as the minimum length of the framebody, because the sum of the minimum length of the frame body, thelength of the PAD field, and the length of 4 bytes of the FCS field isthe integral multiple of the length of the SH field, the PAD field is 4bytes, and the point ((c) of FIG. 10) that is shifted by 8 bytes whichis the length of the SH field from the base point immediately after thecurrent SH field ((b) of FIG. 10), namely, the point ((c) of FIG. 10)that is shifted by 16 bytes from the head of the current SH field ((a)of FIG. 10) is set to the search starting point of the next SH field.The fixed length of 8 bytes of the SH field from the search startingpoint of the next SH field is extracted as the SH field, and the errordetecting is performed while the last 4 bytes of the extracted SH fieldis assumed to be the HCS field.

When the error is found by the error detection using the portion assumedto be the HCS field, the point that is shifted by the fixed length of 8bytes of the SH field from the current search starting point of the SHfield ((c) of FIG. 10) is set to the search starting point of the SHfield ((d) of FIG. 10), the fixed length of 8 bytes of the SH field isextracted as the SH field again, and the error detecting is performedwhile the last 4 bytes is assumed to be the HCS field. When the error isfound again by the error detection using the portion assumed to be theHCS field, the same process is repeated, namely the point that isshifted by the fixed length of 8 bytes of the SH field from the currentsearch starting point of the SH field is set to the search startingpoint of the SH field, the length of the SH field is extracted as the SHfield, and the error detecting is performed on the assumed HCS field.

When the error is not found by the error detection using the portionassumed to be the HCS field, the area that is extracted by the fixedlength of 8 bytes of the SH field is fixed as the SH field, and the FBfield and the FCS field associated with the FB field are extracted. Theprocess to recognize and remove the PAD field is described above.

Therefore, the SH field can be detected even if it is unclear where thenext SH field starts.

In the above process of searching the SH field, when the length of thearea remaining from the base point immediately after the current SHfield is less than the sum of the length of the SH field and twice thesum of the minimum length of the frame body, the length of the FCSfield, and the length of the PAD field in the case of the minimum lengthof the frame body, it can be determined that the next frame set does notexist, and the search process may be ended. As illustrated in FIG. 8,when the length of the FCS field is shorter than the length of the SHfield while the minimum length of the frame body is set to zero, the sumof the length of the FCS field, the minimum length of the frame body,the length of the FCS field, and the length of the PAD field is 8 bytesand equal to the length of the SH field. Therefore, the search processis ended when the area where the process of extracting the frame bodiesis not yet performed is less than 24 bytes in which the length of 8bytes of the SH field is added to 16 bytes that is twice the sum,namely, three times the length of the SH field. On the other hand, whenthe area where the process of extracting the frame bodies is not yetperformed is more than three times the length of the SH field, becausethere is still possibility that frame sets exist, the process ofsearching the next SH field is performed. When the above discussion isreplaced with the discussion of the length of the area remaining fromthe current search starting point of an SH field, because the length ofthe SH field currently assumed exists in addition to three times thelength of the SH field, the question is asked whether the length of thearea remaining from the current search starting point of the SH field isless than four times the length of the SH field.

In the above description, the configuration unit such as theacknowledgement frame in which the frame set is completed by the SHfield as shown in FIG. 2, is not permitted to be mixed. However, whensuch configuration unit is permitted to be mixed, the minimum length ofthe frame body and the length of the FCS field are set to 0 byte (thatis, it is assumed that the frame body and the FCS field do not exist)and the search process is performed while the search starting point ofthe next SH field is set to the point ((b) of FIG. 10) that is shiftedby the fixed length of the SH field from the current search startingpoint of the SH field from the beginning (when the error is detected atthe point (b) of FIG. 10, the search process is performed while thepoint (c) of FIG. 10 is set to the search starting point. The sameprocess will be performed thereafter).

Assuming that the data frame has the format of FIG. 8, a concreteoperation to search the SH field in the case of FIG. 6 is described asfollows. It is assumed that the minimum length of a frame body is 0.When the initial SH field is determined to be erroneous by the HCS fieldthereof, the point shifted by 8 bytes from the base point immediatelyafter the SH field is assumed to be the next search starting point ofthe SH field and the error detection is performed by the newly assumedHCS field portion. In this case, because the SH field is determined tobe erroneous, the search starting point of the SH field is furthershifted by 8 bytes, and the same process is performed. When the final SHfield (designated by SH4) is extracted and determined to be correct bythe HCS field, the FB field is extracted using the length field, thepoint that is not less than the length field and is the minimum integralmultiple of 8 bytes is determined to be the end of the frame set, andthe area of 4 bytes returning from the end of the frame set is extractedas the FCS field. The FB field is determined to be correct by the FCSfield.

The method in which the length of the area where the process ofextracting the frame bodies is not yet performed is used is describedabove as the determination whether the process of searching the SH fieldis continued. When the number of aggregated frames is indicated in theCH field, the number of aggregated frames may be used to determinewhether the process of searching the SH field is continued. The methodin which the number of aggregated frames is used may be combined withthe method in which the length of the area where the process ofextracting the frame bodies is not yet performed is used. When the SHfield is determined to be correct by the HCS field thereof, 1 is countedas the number of frames, and the area where the SH field search fails iscounted as 1. When the count value becomes equal to the number ofaggregated frames, the process of searching the next SH field is ended.In FIG. 6, assuming that the number of aggregated frames of 4 isindicated in the CH field, because the SH field determined to be correctby the HCS field does not exist in the frame sets #1 to #3, only 1 canbe counted as the number of frames, the process of searching the SHfield is continued, and the SH field is determined to be correct by theHCS field in the final frame set #4. The count value of the number offrames is 2 even in the final stage. In FIG. 5, the count value of thenumber of frames is 3 at the frame set #3, and the SH field is searchedimmediately after the frame set #3 on the basis of the relationshipbetween the value of the length field of the SH3 field and the integralmultiple of 8 bytes. However, because the SH4 field is determined to beerroneous at that time, the count value becomes 4, and the SH field isnot further searched.

When there is no restriction to the integral multiple of the length ofthe SH field, assuming that the frame set is always configured in unitsof byte lengths, the portion in which the length of the SH field is usedin the above operation to search the SH field is substituted with 1byte.

Second Embodiment

A second embodiment is based on the first embodiment. In theconfiguration of the first embodiment, the second embodiment has aconfiguration in which the wireless communication terminal on the datatransmission side indicates to the wireless communication terminal onthe data reception side from which sequence number the transmission ofthe data frame is started.

Specifically, for example, a bit indicating the start of the sequencenumber is provided in the SH field. When the wireless communicationterminal on the data transmission side transmits the data frame, the bitin the SH field of a frame set where the initial sequence number is heldis set (that is, the bit is set to 1). In other frame sets, the bit isnot set (that is, the bit is set to 0). Therefore, the wirelesscommunication terminal on the data reception side can obtain thestarting number in recognizing the successively and successfullyreceived maximum sequence number at the same time as the data arereceived, whereby it is not necessary for the wireless communicationterminal on the data reception side to receive the indication of thesequence starting number from the wireless communication terminal on thedata transmission side prior to the data exchange. That is, the dataexchange can instantaneously be performed to improve the communicationefficiency. The wireless communication terminal on the data receptionside sets the sequence starting number to the value of the SN field ofthe SH field to which the bit is set, and sorts the received data itemssuch that their sequence number are in successively increasing orderfrom the sequence starting number. Specifically, the receiving buffer 14of FIG. 3 transfers the data items whose sequence numbers are successivestarting from the data item with the sequence starting number to thereception coordinator 18 and also notifies the SMSN retention unit 16 ofthe maximum sequence number that is successively and successfullyreceived from the sequence starting number. When receiving indication ofthe sequence starting number, the SMSN retention unit 16 overwrites theretaining value by an initial value of (sequence starting number−1), andthen the SMSN retention unit 16 overwrites the initial value by themaximum sequence number that is successively and successfully received.The initial value may be received from the deaggregation/filter unit 12through the reception coordinator 18.

When transmitting an acknowledgement frame in response to the framehaving the bit indicating the start of the sequence number set in the SHfield, by setting the bit (indicated by “recognition of sequence start(SYNC)” in FIG. 11) also in the SH field of the acknowledgement frame,as illustrated in FIG. 11, the wireless communication terminal on thedata transmission side can confirm whether the wireless communicationterminal on the data reception side received the notification of thestart of the sequence number accurately by receiving the acknowledgementframe. Therefore, the wireless communication terminal on the datatransmission side recognizes that the wireless communication terminal onthe data reception side correctly receives the frame sets starting fromthe notified sequence starting number to the successively andsuccessfully received maximum sequence number of which the wirelesscommunication terminal on the data reception side notifies the wirelesscommunication terminal on the transmission side, and the datatransmission including the data retransmission can be scheduledproperly.

This will be described with reference to FIGS. 12 to 14. FIG. 12illustrates the situation where the wireless communication terminal onthe data transmission side transmits a data frame (designated by DATA)containing four frame sets and the wireless communication terminal onthe data reception side transmits an acknowledgement frame (designatedby ACK) in response to the data frame DATA. While the frame format isomitted, the state of the bit (designated by SYNC) indicating the startof the sequence number in each frame set and the value of the sequencenumber (designated by SN) can be seen in the data frame, and the valueof the bit (designated by SYNC) indicating the recognition of theindication of the start of the sequence number and the value of themaximum sequence number (designated by SN) that is successively andsuccessfully received can be seen in the acknowledgement frame.Similarly to the examples of the first embodiment, the reception statusof each frame set or the acknowledgement frame is indicated by the marks“◯” and “x”. In FIG. 12, in order to indicate that the sequence numberis started from the sequence number 101, the bit indicating the start ofthe sequence number is set in the initial frame set (SYNC=1 and SN=101).The bit indicating the start of the sequence number is not set in thesubsequent frame sets because their sequence numbers are not thestarting number (SYNC=0). The wireless communication terminal thatreceives the data frame correctly receives both the SH field and the FBfield of the frame set (SYNC=1 and SN=101) in which the wirelesscommunication terminal is notified of the start of the sequence,correctly receives both the SH field and the FB field of the secondframe set (SYNC=0 and SN=102), detects error in the SH field or the FBfield of the third frame set (SYNC=0 and SN=103), and correctly receivesboth the SH field and the FB field of the fourth frame set (SYNC=0 andSN=104). The wireless communication terminal on the data reception sidetransmits the acknowledgement frame (SYNC=1 and SN=102) that confirmsrecognition of the notification of the start of the sequence number andthe successively and successfully received maximum sequence number tothe wireless communication terminal on the data transmission side afterthe fixed time. When receiving the acknowledgement frame, the wirelesscommunication terminal on the data transmission side performs thetransmission from the frame which has the sequence number larger thanthe successively and successfully received maximum sequence number by 1.In FIG. 13, the frame sets of the sequence number 103 (SYNC=0 andSN=103) and the sequence number 104 (SYNC=0 and SN=104) are transmittedwhile aggregated. Although the frame sets are transmitted whileaggregated in FIG. 13, the frame sets under retransmission may betransmitted separately. However, when the frame sets underretransmission are separately transmitted, it is necessary to transmitthe frames in the order of the sequence numbers. Although only the framesets of the retransmission targets are aggregated in FIG. 13, a newframe set of the sequence number 105 that is not yet transmitted may beaggregated. The plurality of new frame sets may be aggregated whileadded to the frame sets of the retransmission targets as long as the newframe sets have the successive sequence numbers from the sequencenumbers of the frame sets of the retransmission targets. For example,the frame sets having the sequence numbers 105 and 106 may be aggregatedto the data frame of FIG. 13.

The case in which the frame set indicating the start of the sequencenumber is unsuccessfully received, as illustrated in FIG. 14, will bediscussed below.

When the wireless communication terminal on the data reception sidefails to receive the FB field while successfully receiving the SH field,the wireless communication terminal on the data reception side maytransmit an acknowledgement frame having SYNC=1 and SN=100 because thewireless communication terminal on the data reception side recognizesthe sequence starting number 101. That is, the value of (sequencestarting number−1) (that is, initial value of the previous SMSNretention unit 16) is returned when the FB field corresponding to thesequence starting number is unsuccessfully received.

When failing to receive the SH field of the initial frame set, thewireless communication terminal on the data reception side does notrecognize the sequence starting number. However, the wirelesscommunication terminal on the data reception side receives the secondframe set (SN=102) and the fourth frame set (SN=104). Because thecondition to transmit the acknowledgement frame is satisfied, thewireless communication terminal on the data reception side may transmitthe acknowledgement frame while the value retained by the SMSN retentionunit 16 is set in the acknowledgement frame. However, in this case, thewireless communication terminal on the data reception side does notrecognize that the wireless communication terminal on the data receptionside receives the frame set indicating the start of the sequence number,so the bit indicating that the wireless communication terminal on thedata reception side recognizes the notification of the start of thesequence number is not set in the acknowledgement frame (SYNC=0).Therefore, the wireless communication terminal on the data transmissionside recognizes that the wireless communication terminal on the datareception side does not receive the notification of the start of thesequence number, ignores the sequence number indicated in theacknowledgement frame, and performs retransmission from the frame setcorresponding to the sequence starting number with the notification ofthe sequence starting number accompanied. Alternatively, when notrecognizing the sequence starting number, the wireless communicationterminal on the data reception side does not return the value retainedby the SMSN retention unit 16, but return an arbitrary value. Even inthis case, because the bit indicating that the notification of the startof the sequence is recognized is not set (SYNC=0) in the acknowledgementframe, similarly the wireless communication terminal on the datatransmission side recognizes that the wireless communication terminal onthe data reception side does not receive the notification of the startof the sequence number, ignores the sequence number indicated in theacknowledgement frame, and performs retransmission from the frame setcorresponding to the sequence starting number with the notification ofthe sequence starting number accompanied.

Alternatively, when the indication of the sequence starting number isrequired to be in the initial data frame after the connection isestablished, the wireless communication terminal on the data receptionside may not respond to the data frame when that condition is notsatisfied. The wireless communication terminal on the data receptionside may perform the error process in the case of no response. Aftertransmitting the data frame, the wireless communication terminal on thedata transmission side observes whether the acknowledgement frame comesduring the fixed time, and the wireless communication terminal on thedata transmission side can perform the retransmission process whendetermining that the acknowledgement frame does not come.

Therefore, a load on the wireless communication terminal on the datatransmission side can be reduced without receiving the notification ofthe sequence starting number in every physical packet but by receivingthe notification at the beginning of the data exchange.

Third Embodiment

A third embodiment is based on the first embodiment. In theconfiguration of the first embodiment, the third embodiment has aconfiguration in which the process of searching the SH field is endedwhen a certain condition is satisfied even if the area where extractionof frame bodies is not yet performed remains. The condition will bedescribed in detail below. The information retained in the receivingbuffer 14 of FIG. 3 is discarded at the time when the search is ended.

In the first embodiment, the process of searching the next SH field isperformed when the error is detected in the SH field. In the firstembodiment, the SH field is searched when the remaining area is no lessthan the sum of the length of the SH field and twice the sum of theminimum length of the FB field and the length of the FCS field.

At this point, the condition to transmit the acknowledgement frame isthat at least one correct FB field is extracted. The notification of thesuccessively and successfully received sequence number is made in theacknowledgement frame. When the frame sets are required to be always setin the data frame such that their sequence numbers are in successivelyincreasing order, when the one or plurality of frame sets areunsuccessfully received in the first half of the data frame, there is nopossibility of updating the already-retained successively andsuccessfully received sequence number with the received data frame. Inthis case, it is only necessary to acknowledge whether the condition totransmit the acknowledgement frame is satisfied.

Because there is no possibility of updating the already-retainedsuccessively and successfully received sequence number with the receiveddata frame, it is not necessary that the receiving buffer perform theoperation to successively transfer the frame bodies to the next processin the order of the sequence numbers, and it is not necessary to retainthe received data frame in the receiving buffer.

Therefore, it is assumed that the case in which a frame set isunsuccessfully extracted after at least one frame set is correctlyextracted is the condition to end the search of the SH field, namely,the condition to end the process to extract the frame set. Moreparticularly, it is assumed that a first condition is that a certain SHfield is correctly extracted and the FB field extracted using the SHfield is determined to be not erroneous (that is, correct) by the FCSfield associated with the FB field, and it is assumed that a secondcondition is the case in which, in addition to satisfying the firstcondition, the SH field extracted from the area where extraction offrame bodies is not yet performed is determined to be erroneous by theHCS field associated with the SH field or the case in which, in additionto satisfying the first condition, the FB field extracted on the basisof the SH field determined to be not erroneous (that is, correct) isdetermined to be erroneous by the FCS field associated with the FBfield. The process of searching the SH field is not performed when thesecond condition is satisfied.

The information on the frame set retained in the receiving buffer isdiscarded when the ending condition is satisfied.

The process of searching the SH field and the discard of contents of thereceiving buffer will be described with reference to FIGS. 15 to 17.

In FIG. 15, after the CH field is correctly detected, the error isdetected in the SH field (SH1) of the initial frame set by the HCS fieldthereof. Although the subsequent FB field (FB1) is determined to beerroneous, the process is continuously performed to the remaining area.That is, the process of searching the next correct SH field is performedsubsequent to the SH1 field by the method based on the first embodiment.The SH field designated by SH2 in FIG. 15 is correctly extracted, and FBfield FB2 indicated by SH field SH2 is determined to be correct (noterroneous) by the associated FCS field. At this point, the firstcondition is satisfied, the sequence number in SH field SH2 and FB fieldFB2 are transferred from the deaggregation/filter unit 12 of FIG. 3 tothe receiving buffer 14, and the process is continuously performed tothe remaining area. That is, SH field SH3 subsequent to the FCS fieldassociated with FB field FB2 is extracted, and whether the error is notdetected in SH field SH3 is determined using the HCS field of SH fieldSH3. FIG. 15 illustrates the case in which SH field SH3 is determined tobe erroneous, and therefore the second condition is satisfied. Becausethe second condition is satisfied after the first condition issatisfied, the process after the extraction and determination of SHfield SH3 is not performed. That is, although the unprocessed arearemains, the process of searching the SH field is not continued butended unlike in the first embodiment. The items of information on FBfield FB2 and the sequence number corresponding to FB field FB2, whichare retained in the receiving buffer 14 of FIG. 3, are discarded.

FIG. 16 illustrates the case in which, although the first condition issatisfied similarly to the case of FIG. 15 until the process ofextracting SH field SH3, extracted SH field SH3 is determined to be noterroneous (correct) by the HCS field thereof. However, FB field FB3indicated by SH field SH3 is determined to be erroneous by theassociated FCS field, and the second condition is satisfied at thispoint. Because the second condition is satisfied after the firstcondition is satisfied, the process after the extraction anddetermination of FB field FB3 is not performed. That is, although theunprocessed area remains, the process of searching the SH field is notcontinued but ended unlike in the first embodiment. The items ofinformation on FB field FB2 and the sequence number corresponding to FBfield FB2, which are retained in the receiving buffer, are discarded.

FIG. 17 illustrates the case in which the first half of the frame setcan be correctly extracted. Because initial FB field FB1 can becorrectly extracted, the first condition is satisfied, and the processto extract and determine the second SH field SH2 is continued. At thispoint, the sequence number in SH field SH1 and FB field FB1 aretransferred from the deaggregation/filter unit 12 of FIG. 3 to thereceiving buffer 14. The receiving buffer 14 refers to the SMSNretention unit 16 to compare the sequence number of SH field SH1 and thesuccessively and successfully received maximum sequence number, which isretained by the data frame received before the received data frame. Whendetermining that the sequence number of SH field SH1 is larger than theSMSN by 1, the receiving buffer 14 transfers the information on FB fieldFB1 to the upper layer processor 0 through the reception coordinator 18.SH field SH2 is determined to be correct, FB field FB2 is extracted onthe basis of correct SH field SH2, FB field FB2 is also determined to becorrect by the associated FCS field, and the process to extract anddetermine the SH field subsequent to the FCS field is continued. At thispoint, the sequence number in SH field SH2 and FB field FB2 are alsotransferred from the deaggregation/filter unit 12 of FIG. 3 to thereceiving buffer 14. Because the sequence number of FB field FB2 islarger than that of FB field FB1, the receiving buffer 14 also transfersthe information on FB field FB2 to the upper layer processor 0 throughthe reception coordinator 18.

Then, because SH field SH3 is determined to be erroneous, the secondcondition is satisfied. Because the second condition is satisfied afterthe first condition is satisfied, the process after the extraction anddetermination of SH field SH3 is not performed. That is, although theunprocessed area remains, the process of searching the SH field is notcontinued but ended unlike in the first embodiment. In this case,because the frame bodies from FB field FB2 and the items of informationon the sequence numbers associated therewith are not transferred to thereceiving buffer 14, it is not necessary to dare to perform the discardprocess.

In the process of the third embodiment, the frame body and the sequencenumber associated therewith are tentatively transferred from thedeaggregation/filter unit to the receiving buffer, and the informationin the receiving buffer is discarded upon the determination that theprocess is ended. Alternatively, because the information retained by theSMSN retention unit is not updated in the received data frame when thefirst frame set of the received data frame cannot be correctlyextracted, the items of information on the frame bodies of thesubsequent frame sets and the sequence numbers associated therewith maybe configured so as not to be transferred to the receiving buffer. Whenthe frame sets are required to be always set in the data frame such thattheir sequence numbers are in successively increasing order, from thetime when the extraction of the correct initial FB field fails or thetime when the extraction of the correct FB field fails after the FBfields are successively and correctly extracted starting from theinitial FB field, even if the extraction of frame sets is not completedup to the final portion of the received data frame, the items ofinformation on the frame bodies of the subsequent frame sets and thesequence numbers associated therewith are not transferred to thereceiving buffer, or the retention of the information is stopped in thereceiving buffer.

Therefore, the receiving buffer 14 does not retain redundant items ofinformation except the SMSN set in the acknowledgement frame and theinformation necessary for the SMSN retention unit 16, so that the use ofthe memory can be reduced on the data reception side compared with themethod for responding to the plurality of data items of the related art.The buffer management can be facilitated to reduce implementation loads.The reduction of the implementation load leads to decreasing a risk ofgenerating bugs in implementation.

The case in which the frame sets are required to be always set in thedata frame such that their sequence numbers are in successivelyincreasing order is described above. Alternatively, even if the sequencenumbers are randomly set, the process may be ended under theabove-described conditions. At this point, the SMSN cannot always beupdated, although the SMSN could be updated unless the process is ended.However, because the condition to transmit the acknowledgement frame issatisfied, the wireless communication terminal on the data receptionside can notify the wireless communication terminal on the datatransmission side that at least one correct frame set is received.

Therefore, the redundant process of searching the SH field can bestopped after the condition to transmit the acknowledgement frame issatisfied, and power consumption can be reduced.

Fourth Embodiment

A fourth embodiment is based on the third embodiment. The fourthembodiment relates to a condition to end the process even if theunprocessed area sufficiently remains. In the fourth embodiment, it isnot always necessary that the frame sets be set in the data frame suchthat their sequence numbers are in successively increasing order, butthe processing is ended after the SMSN is updated at least once.Specifically, the first condition of the third embodiment is changed.

It is assumed that the first condition is that a certain FB field isdetermined to be not erroneous (correct) by the FCS field associatedtherewith and the SN field in the SH field corresponding to the FB fieldupdates the successively and successfully received maximum sequencenumber retained in the SMSN retention unit 16 of FIG. 3. The process ofsearching the SH field is continued until the successively andsuccessfully received maximum sequence number is updated on the basis ofthe received data frame. After the SMSN is updated at least once, thenext process of searching the SH field is ended, even if the unprocessedarea remains when the SH field is determined to be erroneous or when theFB field corresponding to the SH field is determined to be erroneouswhile the SH field is determined to be correct. The time when thereceiving buffer performs the discard process is when the secondcondition is satisfied after the first condition is satisfied.

For example, it is assumed that the second frame set is successfullyreceived as illustrated in FIG. 15 and the sequence number thereofupdates the successively and successfully received maximum sequencenumber retained by the SMSN retention unit 16. At this point, the firstcondition is satisfied, and the subsequent process is ended at the timewhen SH field SH3 is determined to be erroneous similarly to the thirdembodiment. When receiving FB field FB2 from the deaggregation/filterunit 12 of FIG. 3, the receiving buffer 14 refers to the value retainedby the SMSN retention unit 16. Because the sequence number correspondingto FB field FB2 is larger than the value by 1, the receiving buffer 14transfers FB field FB2 to the upper layer processor 0 through thereception coordinator 18. Then, as the process is ended with respect tothe received data frame in the deaggregation/filter unit 12, thereceiving buffer 14 becomes empty because the items of information onthe FB field and the SN field are not transferred to the receivingbuffer 14.

For example, although the second frame set is successfully received asillustrated in FIG. 15, the successively and successfully receivedmaximum sequence number retained in the SMSN retention unit 16 is notupdated by the sequence number of the second frame set.

At this point, because the first condition is not satisfied, unlike inthe third embodiment, the process of searching the subsequent SH fieldis continued even if SH field SH3 is determined to be erroneous.Although the first and second frame sets are correctly received asillustrated in FIG. 17, when, for example, the successively andsuccessfully received maximum sequence number by the data frame that isreceived prior to the current received data frame is 100, the firstframe set has the sequence number of 103, and the second frame set hasthe sequence number of 104, because the successively and successfullyreceived maximum sequence number is not yet updated by the currentreceived data frame, unlike in the third embodiment, the process ofsearching the subsequent SH field is continued even if SH field SH3 isdetermined to be erroneous.

Even if the data items are randomly set in the physical packet, thecondition to transmit the acknowledgement frame can be satisfied, andthe redundant process of searching the SH field can be stopped after thewireless communication terminal on the data reception side extracts thesignificant data, so that the power consumption can be reduced.

Fifth Embodiment

A fifth embodiment is based on the first embodiment. In theconfiguration of the first embodiment, the fifth embodiment has aconfiguration in which the information retained by the receiving bufferis discarded every time the reception process of a data frame is ended.

In the first embodiment, because the wireless communication terminal onthe data transmission side is notified of the successively andsuccessfully received maximum sequence number, the frame setcorresponding to the sequence number larger than the successively andsuccessfully received maximum sequence number becomes the target of theretransmission in the wireless communication terminal on the datatransmission side. Even if the frame sets are retained in the receivingbuffer while some sequence numbers are partially skipped in the wirelesscommunication terminal on the data reception side, the wirelesscommunication terminal on the data transmission side performs theretransmission including the already-received frame sets. Therefore, thewireless communication terminal on the data reception side receives theoverlapping frame sets. Accordingly, there is no problem even if theportion of the receiving buffer where the sequence numbers are partiallyskipped is discarded.

This will be described with reference to FIG. 18. FIG. 18 conceptuallyillustrates items of information on the receiving buffer 14 and the SMSNretention unit 16 of FIG. 3. In FIG. 18, the items of information on theframe bodies corresponding to the sequence numbers 102 and 104 areretained in the receiving buffer 14, and the successively andsuccessfully received maximum sequence number is 100 by referring to theSMSN retention unit 16. Because the frame sets are successive up to thesequence number of 100, they are passed to the next process, and withthe receiving buffer being managed in the order of the sequence numbers,the frame bodies corresponding to the sequence numbers 101 and 103 arenot yet received. At this point, in the operation of the fifthembodiment, the items of information on the frame bodies correspondingto the sequence numbers 102 and 104 retained by the receiving buffer arediscarded when the process is ended with respect to the received dataframe. Specifically, when recognizing that the processing is completedto the received data frame, the deaggregation/filter unit 12 of FIG. 3indicates to the reception coordinator 18 of the end of processing thereceived frame. When receiving the indication of the end of processingthe received frame from the deaggregation/filter unit 12, the receptioncoordinator 18 receives the frame bodies up to the successively andsuccessfully received maximum sequence number from the receiving buffer14 and issues an instruction to delete the retained information to thereceiving buffer 14. Alternatively, the reception coordinator 18 doesnot issue the instruction to the receiving buffer, but receptioncoordinator 18 may delete the information retained by the receivingbuffer.

Even if the frame sets are set in the data frame while the sequencenumbers are not always in successively increasing order, whether thereis a sequence number that becomes the SMSN can securely be confirmed upto the final portion of the data frame, and it is not necessary toretain the unnecessary information in the receiving buffer after thereceiving process. Therefore, the use of the memory can be reduced.

Sixth Embodiment

A sixth embodiment can be applied to the first to fifth embodiments. Ina configuration of the sixth embodiment, a criterion for determinationwhether the wireless communication terminal on the data transmissionside performs the transmission within the proper range of sequencenumbers is provided in the wireless communication terminal on the datareception side.

In the first embodiment, the plurality of frame sets can be set in onedata frame while aggregated. On the other hand, the wirelesscommunication terminal on the data reception side performs the operationto sequentially transfer the frame sets to the upper layer process suchthat their sequence numbers are in successively increasing order.Therefore, it is necessary to take into account the range of thesequence numbers of the frame sets including the new and retransmittedframe sets in the wireless communication terminal on the datatransmission side, namely, a sliding window on the data transmissionside, and a receiving buffer size in the wireless communication terminalon the data reception side. It is necessary that at least the number offrame sets that can be retained by the receiving buffer size be greaterthan or equal to the range of the sliding window on the datatransmission side. Preferably a width of the sliding window on the datatransmission side is equal to the number of frame sets that can beretained by the receiving buffer size. Therefore, the necessary andsufficient condition is obtained on both the data transmission side andthe data reception side.

For example, it is assumed that both the width of the sliding window onthe data transmission side and the receiving buffer can correspond tofour frame sets. Accordingly, there is no problem when the wirelesscommunication terminal on the data reception side receives the framesets up to the sequence number that is larger than the successively andsuccessfully received maximum sequence number by 4. On the other hand,when wireless communication terminal on the data reception side receivesthe frame set having the sequence number that is larger than the SMSN by5 or more, the process of successively transferring the information onthe frame body from the retained successively and successfully receivedmaximum sequence number to the upper layer processor 0 cannot beperformed. For example, it is assumed that the frame set having thesequence number 105 is received while the successively and successfullyreceived maximum sequence number is 100, and it is assumed that theframe set having the sequence number 105 is retained in the receivingbuffer. When four frame sets having sequence numbers 101 to 104 arereceived, one of the frame sets overflows from the receiving buffer, andtherefore the process of successively transferring the information onthe frame body to the upper layer processor 0 cannot be performed.Accordingly, when receiving the data frame including the frame sethaving the sequence number that is larger than the value in which thereceiving buffer size (in this case, 4) is added to the successively andsuccessfully received maximum sequence number retained at the stage atwhich the preceding received data frame is processed, the wirelesscommunication terminal on the data reception side determines that thedata frame violates continuity, in other words, determines violation ofthe sliding window, and performs the error process.

The wireless communication terminal on the data transmission sidecontrols the sliding window on the data transmission side on the basisof the successively and successfully received maximum sequence numberwhich the wireless communication terminal on the data reception sidenotifies the wireless communication terminal on the data transmissionside in the acknowledgement frame. In the sixth embodiment, assumingthat the sliding window has the width of 4 equal to the receiving buffersize while the successively and successfully received maximum sequencenumber received from the wireless communication terminal on the datareception side is 100, a starting point Win_s of the sliding window ismatched with 100+1, namely, 101, and an ending point Win_e of thesliding window is 100+4, namely, 104. Therefore, only the frame sets ofthe sequence numbers 101 to 104 are transmitted while set in the dataframe. The frame sets may be transmitted from any frame set within thesliding window, but preferably the frame sets are transmitted in theorder of the sequence numbers. It is not necessary to set all the framesets within the sliding window in the data frame at once. If thesequence numbers are within the sliding window, the number of frame setsset in the same data frame is arbitrarily determined. Desirably theframe sets having the successive sequence numbers from the startingpoint Win_s of the sliding window are set in one data frame, althoughthe frame sets may randomly be set in the data frame. Therefore, thedata that are efficiently received can be transferred to the upper layerprocessor 0 in the order of the sequence numbers in the wirelesscommunication terminal on the data reception side.

On the other hand, when the wireless communication terminal on the datatransmission side does not receive the acknowledgement frame or cannotcorrectly receive the acknowledgement frame while the wirelesscommunication terminal on the data reception side transmits thesuccessively and successfully received maximum sequence number 100 bythe acknowledgement frame, the wireless communication terminal on thedata transmission side does not update the sliding window on the datatransmission side. Accordingly, at this point, the wirelesscommunication terminal on the data transmission side and the wirelesscommunication terminal on the data reception side are not synchronizedwith each other, but the wireless communication terminal on the datatransmission side transmits the data frame again on the basis of the oldsliding window. When the successively and successfully received maximumsequence number given by the preceding acknowledgement frame is 96 andis correctly received, the frame sets of the sequence numbers 97 to 100are transmitted in the data frame, for example. In the wirelesscommunication terminal on the data reception side, frame sets includedin a data frame that are transmitted on the basis of the old slidingwindow should not be detected as the violation of continuity, in otherwords, the violation of the sliding window. On the other hand, a dataframe including frame sets having the sequence numbers smaller than thatof the frame sets transmitted on the basis of the old sliding windowshould be detected as the violation of continuity. However, thedetermination is made when the preceding acknowledgement frame iscorrectly received. When receiving a data frame including frame setshaving the sequence numbers that are less than or equal to the value inwhich the receiving buffer size (in this case, 4) is subtracted from thecurrently retained successively and successfully received maximumsequence number, the wireless communication terminal on the datareception side determines that the data frame violates continuity. Thatis, when a frame set having the sequence number 96 or less is receivedwhile the frame sets up to the sequence number 100 are received already,the wireless communication terminal on the data transmission sideperforms transmission while ignoring the width of the sliding window onthe data transmission side. Even if the minimum sequence number in adata frame is 97, when the data frame also includes a frame set havingthe maximum sequence number 101 or more, the wireless communicationterminal on the data reception side determines that the data frameviolates continuity. In such cases, the error process is started aspreviously described.

In the configuration of the wireless communication terminal of FIG. 3,the detection of the violation of continuity, in other words, theviolation of the sliding window in the wireless communication terminalon the data reception side may be processed as follows.

Detection of Violation when Sequence Number being Excessively Small:

Example 1: The deaggregation/filter unit 12 ends the reception of thedata frame while extracting the minimum sequence number in the dataframe, and the deaggregation/filter unit notifies the receptioncoordinator 18 of the minimum sequence number when transmitting thenotification of the end of the reception frame process to the receptioncoordinator 18. When receiving the notification of the end of thereception frame process from the deaggregation/filter unit 12, thereception coordinator 18 extracts the minimum sequence number in thenotification to compare the minimum sequence number with the SMSNretained by the SMSN retention unit 16. When the minimum sequence numberis less than or equal to the value in which the receiving buffer size issubtracted from the SMSN, the error process is started.

Example 2: Alternatively, the deaggregation/filter unit 12 transmits thenotification of the start of the data frame reception and thenotification of the end of the data frame reception to the receivingbuffer 14. When receiving the notification of the start of the dataframe reception, the receiving buffer 14 retains the minimum sequencenumber among the sequence numbers input from the deaggregation/filterunit 12 from that point of time. When receiving the notification of theend of the data frame reception, the receiving buffer 14 compares theminimum sequence number with the SMSN retained by the SMSN retentionunit 16. When the minimum sequence number is less than or equal to thevalue in which the receiving buffer size is subtracted from the SMSNretained by the SMSN retention unit 16, the receiving buffer 14 issuesthe instruction to perform the error process to the receptioncoordinator 18.

Following Example 1, the error process can be performed while thetransmission of the acknowledgement frame is stopped. Following Example2, the error process is started after the acknowledgement frame istransmitted. In order to stop the transmission of the acknowledgementframe, the reception coordinator 18 provides a procedure to confirmwhether the comparison process in the SMSN retention unit 16 normallyended when the reception coordinator 18 receives the notification of theend of the reception frame process from the deaggregation/filter unit12.

Detection of Violation when Sequence Number being Excessively Large:

The deaggregation/filter unit 12 transmits the notification of the startof the data frame reception to the receiving buffer 14. When receivingthe notification of the start of the data frame reception from thedeaggregation/filter unit 12, the receiving buffer 14 obtains the SMSNfrom the SMSN retention unit 16. When the sequence number that is inputfrom the deaggregation/filter unit 12 after the notification of thestart of the data frame reception is larger than the value in which thereceiving buffer size is added to the obtained SMSN, the receivingbuffer 14 issues the instruction to perform the error process to thereception coordinator 18.

At this point, in the error process, preferably the connection to thewireless communication terminal on the data transmission side isreleased by transmitting a management frame for release (disconnection).All the frame sets included in the data frame in which the violation ofcontinuity is detected are discarded.

As described above, the sequence number is allocated by the integralcounter, and the integral counter performs a cyclic operation in whichthe count is performed from the minimum value (0) when the count valuereaches the maximum value. Accordingly, although the sequence numbersare expressed “small” or “large”, the actual values do not become smallor large at a boundary at which the count value returns to the minimumvalue. For example, the integral counter has the maximum value of 255,the receiving buffer size is 4, the currently retained SMSN is 253, andthe SMSN is transmitted while set in the acknowledgement frame. At thispoint, the case in which the next received data frame includes the framesets having only the sequence numbers 250, 251, 252, and 253, or thecase in which the next received data frame includes the frame setshaving only the sequence numbers 254, 255, 0 (=256−256), and 1(=257−256) is determined to be normal, and other cases are determined tobe violation.

In order to have the wireless communication terminal on the datatransmission side and the wireless communication terminal on the datareception side common recognition of the sliding window width and thereceiving buffer size, a method in which the wireless communicationterminal on the data transmission side and the wireless communicationterminal on the data reception side notifies each other of the slidingwindow width and the receiving buffer size using the management framesbefore data frames are transmitted can be used, for example. By at leastnotifying of the receiving buffer size of the wireless communicationterminal on the data reception side, the wireless communication terminalon the data transmission side can set the sliding window width less thanor equal to the indicated receiving buffer size. Alternative methodwould be that, the wireless communication terminal on the datatransmission side and the wireless communication terminal on the datareception side do not notify each other using the management frames, butthe sliding window width and the receiving buffer size are uniquelyspecified as the system.

Therefore, the operation to transfer data to the upper layer processor 0in the order of the sequence numbers can be guaranteed in the wirelesscommunication terminal on the data reception side.

Seventh Embodiment

A seventh embodiment can basically be applied to the first embodiment orthe sixth embodiment. In the configuration of the sixth embodiment, thesituation in which the receiving buffer of the wireless communicationterminal becomes unable to receive a new frame set (i.e., becomes full)is considered.

In the receiving buffer of the wireless communication terminal thatreceives data frames, when the frame bodies having the successivesequence numbers are received, usually the frame bodies are passed tothe next process. In the first embodiment, the receiving buffer 14 ofFIG. 3 transfers the frame bodies corresponding to the successivesequence numbers to the upper layer processor 0 through the receptioncoordinator 18. At this point, when the receiving buffer 14 transfersthe frame body to the reception coordinator 18, for example, it isassumed that the reception coordinator 18 notifies the receiving buffer14 of whether the frame body is normally received and the receivingbuffer 14 recognizes whether the frame body is normally transferred tothe reception coordinator 18 by the notification. Even in transferringvarious data items including the frame body information between thereception coordinator 18 and the upper layer processor 0, it is assumedthat whether the transfer of the data items is completed normally isrecognized on the basis of a notification signal between the receivingbuffer 14 and the reception coordinator 18. For example, when thereception coordinator 18 can not transfer the previous frame body to theupper layer processor 0 because the process in the upper layer processor0 is delayed, even if there are frame bodies corresponding to thesuccessive sequence numbers in the receiving buffer 14, the frame bodiescannot be transferred to the reception coordinator 18 (a notificationsignal of failure is returned even if the frame bodies are transferred),and the frame bodies (and their corresponding sequence numberinformation) are still retained by the receiving buffer. In thesituation, even if the wireless communication terminal on the datatransmission side properly controls the sliding window on the datatransmission side to transmit a data frame including frame bodies havingproper sequence numbers, possibly the receiving buffer in the wirelesscommunication terminal on the data reception side is full, and thereceiving buffer cannot receive the new data frame.

In such case, in the seventh embodiment, because the transfer of theframe bodies corresponding to the successive sequence numbers from thereceiving buffer 14 to the reception coordinator 18 is not completed,the SMSN retention unit 16 does not receive notification of the sequencenumbers. That is, the SMSN retention unit 16 does not update thesuccessively and successfully received maximum sequence number. Thesuccessively and successfully received maximum sequence number that isset in the acknowledgement frame transmitted after the reception of thedata frame is completed is the sequence number retained by the SMSNretention unit 16, namely, the sequence number corresponding to theframe body that the receiving buffer 14 was able to transfer normally tothe next process.

For example, as illustrated in FIG. 19, it is assumed that the SMSNretention unit 16 retains 100 as the successively and successfullyreceived maximum sequence number while the empty receiving buffer 14having the receiving buffer size of 4 can receive data frames. It isalso assumed that, when a data frame including frame bodiescorresponding to sequence numbers 101 to 104 is received, thedeaggregation/filter unit 12 can correctly extract the frame bodiesexcept the frame body having the sequence number 103. The frame bodiescorresponding to the sequence numbers 101, 102, and 104 are transferredto the receiving buffer 14 along with the sequence numbers thereof, andthe receiving buffer 14 transfers the frame body corresponding to thesequence number 101 to the next process because the sequence number 101is larger than the sequence number 100 retained by the SMSN retentionunit 16 by 1 and successive. Then the SMSN retention unit 16 retains thevalue of 101. It is assumed that the transfer process is unsuccessfullyperformed although the next frame body has the successive sequencenumber 102. Therefore, the acknowledgement frame is transmitted whilethe sequence number 101 is set in the acknowledgement frame, asillustrated in FIG. 19, instead of setting the sequence number 102 inthe acknowledgement frame. In response to the acknowledgement frame,possibly the wireless communication terminal on the data transmissionside transmits a data frame in which the frame sets corresponding to thesequence numbers 102 to 104 of the retransmission targets and a frameset corresponding to a new sequence number 105 are set, as illustratedin FIG. 20. However, when the receiving buffer can not pass the framebody corresponding to the sequence number 102 to the next process, evenif the receiving buffer could pass all the sequence numbers 102 to 105to the next process because all the frame sets are received correctly,the acknowledgement frame in which the sequence number 101 is set istransmitted.

The pieces of information on the sequence numbers 102 and 104 in thereceiving buffer on the right hand side of FIG. 19 may be discarded atthe same time as the acknowledgement frame is transmitted. In FIG. 20,the frame sets corresponding to the sequence number 102 or more may bediscarded because the frame sets are the retransmission targets.

When receiving an acknowledgement frame in which the successively andsuccessfully received maximum sequence number is not increased by aplurality of times, the wireless communication terminal on the datatransmission side presumes that the receiving buffer of the wirelesscommunication terminal on the data reception side can not pass the framebody to the next process, and the wireless communication terminal on thedata transmission side can perform the control so as to wait thetransmission of the data frame for a while. When the receiving bufferfalls in the situation in which the receiving buffer can not pass theframe bodies having the successive sequence numbers to the next process,a time until the situation is solved is estimated, the estimated time istransmitted by an acknowledgement frame or by a different frame insteadof an acknowledgement frame, and the wireless communication terminal onthe data reception side and the wireless communication terminal on thedata transmission side may perform a power saving operation during theestimated time. For example, the technique disclosed in JP-A No.2010-259171 (KOKAI) may be used to estimate the time until the situationis solved, when the receiving buffer falls in the situation in which thereceiving buffer can not pass the frame bodies having the successivesequence numbers to the next process. That is, the technique ofestimating the waiting time until the free space in which the payloaddata can be stored is secured in the receiving buffer may be used in thewireless communication device that generates a buffer-full signal whenthe size of the received payload data is larger than a free space in thereceiving buffer. The waiting time can be estimated on the basis of thetime for which data are transferred from the receiving buffer to anupper layer protocol or a host system or the time required for anoperating sequence of the storage to which data are transferred.Specifically, the waiting time can be estimated on the basis of arelationship between a preparation time for writing data in a hard diskdrive or a flash memory, data amount, a data transfer rate, and atransfer time in an interface of a USB (Universal Serial Bus) device ora PCI (Peripheral Component Interconnect) device, etc.

In the seventh embodiment, the receiving buffer 14 transfer the framebody to the upper layer processor 0 through the reception coordinator18. Alternatively, the frame body may directly be transferred to theupper layer processor 0. At this point, the transfer of the notificationsignal relating to the reception of the frame body takes place betweenthe receiving buffer 14 and the upper layer processor 0 instead ofbetween the receiving buffer 14 and the reception coordinator 18.

Therefore, the situation in which the receiving buffer of the wirelesscommunication terminal becomes unable to receive a new frame set (i.e.,becomes full) can be dealt with in the wireless communication terminalon the reception side of data frames.

Eighth Embodiment

An eighth embodiment is based on the first embodiment. The eighthembodiment specifies the operation in the case of existence of thewireless communication terminal that cannot correspond to receiving adata frame having a plurality of frame sets aggregated given by thefirst embodiment. For example, the eighth embodiment relates tocoexistence with a wireless communication terminal that is capable ofreceiving a data frame having aggregated frame sets up to two, but notcapable of aggregated frame sets more than that.

Even if the wireless communication terminal of the first embodimentpossibly transmits the data to the other wireless communication terminalthat is not capable of receiving a data frame having aggregated framesets more than two, the wireless communication terminal of the firstembodiment recognizes a capability of the other wireless communicationterminal of the communication pair in a procedure to establish theconnection to the other wireless communication terminal of thecommunication pair before data frames are transmitted, which allows theproper configuration of the data frame to be used. For example, inestablishing a connection, it is assumed that one of the wirelesscommunication terminals transmits the management frame of a connectionrequest, and it is assumed that the wireless communication terminal thatreceives the management frame transmits the management frame of aconnection response when accepting the connection request. When theversion corresponding to each of the wireless communication terminals isdescribed in each of the management frames, when there is a differencebetween the versions, the wireless communication terminal having thehigher version can recognize that the reception can be performed up towhich data frame in the lower version, and the transmission may berestricted to the method corresponding to the lower version when dataframes are transmitted.

Here, it is assumed that the format in which the notification of thesequence number is made like the first embodiment is also used for theacknowledgement frame in the lower version. When the wirelesscommunication terminal having the higher version is the data receptionside, there is no problem in transmitting an acknowledgement frame inresponse to a data frame containing only one frame body on the basis ofthe first embodiment. Because frame bodies are transmitted in the orderof the sequence numbers, when a data frame including only one frame bodyis correctly received, the successively and successfully receivedmaximum sequence number is updated with the sequence number relating tothe frame body. Therefore, when an acknowledgement frame is transmittedwhile the sequence number is set in the acknowledgement frame, thewireless communication terminal on the data transmission side cannormally process the acknowledgement frame because the wirelesscommunication terminal on the data transmission side normally receivesthe acknowledgement frame in the lower version. Even if the wirelesscommunication terminal which can only include two frame bodies in a dataframe is the data transmission side while the wireless communicationterminal that can receive a data frame including three or more framebodies is the data reception side, the acknowledgement frame may betransmitted on the basis of the first embodiment. This is because thewireless communication terminal on the data transmission side recognizesthat the sequence numbers up to the indicated sequence number arenormally received by the wireless communication terminal on the datareception side to appropriately determine the retransmission.

Even if the wireless communication terminal having the lower versionreceives a data frame or an acknowledgement frame based on the firstembodiment as a third party, because the Rx UID of the CH header doesnot specify the wireless communication terminal, the data frame or theacknowledgement frame is discarded.

Even in the case of a data frame, in which the frame sets are aggregatedwith the number of frame sets that cannot be dealt with by the wirelesscommunication terminal on the data reception side, being transmitted, ifthe number of aggregated frame sets is described in the SH field, forexample, whether the number of aggregated frame sets is less than orequal to the number of frame sets that can be dealt with can beconfirmed to perform a proper process. For example, the frame sets up tothe number of frame sets that can be dealt with may be accepted at thereception process. However, because this becomes a similar situation tothat of the sixth embodiment, preferably the management framedisconnecting the connection, in other words, the management framereleasing the communication link, is transmitted to the wirelesscommunication terminal on the data transmission side. Preferably themanagement frame disconnecting the connection notifies of the reasonsuch as the version is different, or such as the data frame includingthe number of frame sets exceeding the number of frame sets that can bedealt with is transmitted. Therefore, after selecting properly thetransmission method, the wireless communication terminal on the datatransmission side that receives the management frame can exchangemanagement frames for the procedure to set up reconnection with theother wireless communication terminal of the communication pair toresume the transmission of data frames.

Even if there is a wireless communication terminal that is not capableof the first embodiment, the proper process can be performed between thewireless communication terminal that is capable of the first embodimentand the wireless communication terminal that is not capable of the firstembodiment, and the wireless communication system does not break down.

Ninth Embodiment

A ninth embodiment basically relates to a modification of the seventhembodiment. In the seventh embodiment, only the sequence number that canbe transferred from the receiving buffer 14 to the next process isretained as the successively and successfully received maximum sequencenumber. In the ninth embodiment, the sequence number that cannot betransferred from the receiving buffer 14 to the next process but is themaximum sequence number further successive is also retained, and thelatter sequence number is set in the acknowledgement frame.

For the sake of convenience, the SMSN that can be transferred from thereceiving buffer 14 to the next process is expressed by SMSN_B, and thesuccessively and successfully received maximum sequence number with thestatus of the receiving buffer 14 taken into account is expressed bySMSN_R.

Similarly to the above-described embodiments, SMSN_B is the sequencenumber corresponding to the frame body that is retained by the SMSNretention unit 16 at the time when the transfer is successfullyperformed when the frame bodies are transferred from the receivingbuffer 14 to the reception coordinator 18 such that the sequence numbersare increased one by one.

SMSN_R is the successively and successfully received maximum sequencenumber when the sequence numbers of the frame sets retained by thereceiving buffer 14 are taken into account. In the receiving buffer 14,the frame sets are managed on the basis of the sequence numbers. Whenthe frame body having the successive sequence number from SMSN_B iscorrectly received in the receiving buffer 14, the value of SMSN_R isupdated, and the SMSN retention unit 16 is notified of the SMSN_R. Whena processing time for which the receiving buffer 14 transfers the framebody to the reception coordinator 18 is ideally eliminated, SMSN_Rbecomes identical to SMSN_B. However, actually there is a processingdelay. Even if the sequence numbers are successive like the situation inthe seventh embodiment, sometimes some of the frame bodies cannot betransferred from the receiving buffer 14 to the reception coordinator18. In such case, the value of SMSN_R differs from the value of SMSN_B.

The reception coordinator 18 concurrently transmits the value of SMSN_Rwhen issuing the instruction to transmit the acknowledgement frame tothe transmission processor 20, and the transmission processor 20transmits the acknowledgement frame with the value of SMSN_R set in theSN field of.

The specific operation will be described with reference to FIGS. 21 to23. The receiving buffer size is set to 4 similarly to the seventhembodiment of FIGS. 19 and 20. In FIG. 21, the receiving buffer 14 isempty and in a receivable state, and SMSN_B 100 and SMSN_R 100 areretained in the SMSN retention unit 16. It is also assumed that, when adata frame including frame bodies corresponding to sequence numbers 101to 104 is received, the deaggregation/filter unit 12 can correctlyextract the frame bodies except the frame body having the sequencenumber 103. The frame bodies corresponding to the sequence numbers 101,102, and 104 are transferred to the receiving buffer 14 along with thesequence numbers thereof, and the receiving buffer 14 transfers theframe body corresponding to the sequence number 101 to the next processbecause the sequence number 101 is larger than SMSN_B 100 retained bythe SMSN retention unit 16 by 1 and successive. Then SMSN_B 101 andSMSN_R 101 are retained in the SMSN retention unit 16. Because the nextframe body corresponding to the sequence number 102 is also successive,the receiving buffer 14 updates SMSN_R 101 of the SMSN retention unit 16with 102. However, the operation of transferring the frame body to thenext process is not yet accepted. Accordingly, SMSN_B is 101, and SMSN_Ris 102. After the data frame is received, the acknowledgement frame inwhich the sequence number 102 is set is transmitted as illustrated inFIG. 21. At this point, the wireless communication terminal on the datareception side may discard the frame set corresponding to the sequencenumber 104. When the width of the sliding window on the transmissionside is set to 4 equal to the receiving buffer size of the wirelesscommunication terminal on the data reception side, in response to theacknowledgement frame, possibly the wireless communication terminal onthe data transmission side transmits the data frame in which the framesets corresponding to the sequence numbers 103 and 104 of theretransmission targets and frame sets corresponding to new sequencenumbers 105 and 106 are set as illustrated in FIG. 22. In the situationin which the frame body corresponding to the sequence number 102 is notpassed to the next process even if the wireless communication terminalon the data reception side was able to receive all the frame setscorrectly, SMSN_R becomes 105 that is the maximum sequence number thatcan be retained by the receiving buffer 14 while SMSN_B is 101. Theframe set corresponding to the sequence number 106 cannot be set in thereceiving buffer 14, but discarded. The SN field of the acknowledgementframe to be transmitted is set to 105. It is assumed that, in responseto the acknowledgement frame of FIG. 22, the wireless communicationterminal on the data transmission side transmits a data frame in whichthe frame set corresponding to the sequence number 106 that becomes theretransmission target and frame sets corresponding to new sequencenumbers 107 to 109 are set, as illustrated in FIG. 23. In the situationin which the frame body corresponding to the sequence number 102 is notpassed to the next process even if the deaggregation/filter unit 12 wasable to receive all the frame sets correctly in the wirelesscommunication terminal on the data reception side, SMSN_R is 105 whilethe SMSN_B is 101 because the receiving buffer 14 cannot retain the newframe sets, namely, the frame sets corresponding to the sequence numbers106 to 109. The acknowledgement frame in which the 105 is set in the SNfield is transmitted again.

The operation similar to that of the seventh embodiment is performedafter the sequence number which the acknowledgement frame indicates doesnot increase.

According to the ninth embodiment, the acknowledgement frame istransmitted while the value of SMSN_R is set in the SN field of theacknowledgement frame. Therefore, the wireless communication terminal onthe data transmission side can perform the transmission including theretransmission of the frame set up to the range that is permissible inthe receiving buffer 14, and the communication efficiency can beimproved.

As described above, according to the ninth embodiment, wirelesscommunication terminal on the data transmission side is able to transmitframe sets equal to or more than the number of frame sets that can beretained by the receiving buffer 14. According to the sixth embodiment,this is the violation of continuity in the wireless communicationterminal on the data reception side. However, this is not the violationof continuity because the wireless communication terminal on the datatransmission side controls the sliding window on the basis of the valueof the SN field described in the acknowledgement frame. Accordingly, inthe ninth embodiment, when the data frame including the frame set havingthe sequence number larger than the value of the SN field described inthe acknowledgement frame, namely, the sequence number of SMSN_R, by thereceiving buffer size or more is received, the wireless communicationterminal on the data transmission side makes the determination of theviolation of continuity to start the error process. In FIGS. 22 and 23,some frame sets can not be hold in the receiving buffer 14. However,because the frame sets fall within the range of SMSN_R+4, the frame setsdo not violate continuity. For example, in FIG. 22, the determination ofthe violation of continuity is made when the data frame in which theframe set corresponding to the sequence number 107 is also set isreceived because SMSN_R=102.

Tenth Embodiment

A tenth embodiment can be applied to the first to ninth embodiments. Thetenth embodiment relates to processing when fragmented data arereceived.

When the data are fragmented, the fragmented data items are set in theplurality of frame sets on the basis of the first embodiment, and theirsequence numbers are in successively increasing order. A more-fragmentfield (hereinafter referred to as an FM field) in which the informationon the fragment is set is provided in the SH field. The FM field is setto 0 in the frame set when the data are not fragmented, or when theframe set contains the final fragment. In other cases, namely, whenthere are continued fragmented data, the FM field is set to 1.Accordingly, preferably the size of the FM field is set to 1 bit.

In the wireless communication terminal on the data reception side, thereceiving buffer 14 transfers the frame bodies to the receptioncoordinator 18 in the order in which their sequence numbers successivelyincrease, and the value of FM field is also transferred at the sametime. Therefore, the reception coordinator 18 performs defragmentprocess of combining the current frame body with the frame bodycorresponding to the next sequence number as one data item when the FMfield is set to 1. When the FM field is set to 0, the frame body isdirectly transferred to the upper layer processor 0 without waiting forthe next frame body.

When frame sets are directly transferred from the receiving buffer 14 tothe upper layer processor 0, the defragment process may be provided inthe upper layer processor 0.

Therefore, even if the data frame in which the data are fragmented isreceived, the wireless communication terminal on the data reception sidecan recover the original data from the fragmented data, namely, performthe defragment process.

Eleventh Embodiment

An eleventh embodiment can be applied to the first to tenth embodiments.The eleventh embodiment relates to conditions to generate and transmitthe acknowledgement frame. Specifically, the acknowledgement frame isgenerated and transmitted when at least one subheader field isdetermined to be correct by the HCS field in the received data frame.

In the configuration of the wireless communication terminal of the firstembodiment with reference to FIG. 3, the deaggregation/filter unit 12 ischanged as follows. That is, the deaggregation/filter unit 12 starts theprocessing to the received frame and issues the instruction to start thepreparation of the acknowledgement frame to the reception coordinator 18when the information in the SH field is correctly extracted and that isthe first one from the received frame.

For example, the state of FIG. 7 in the first embodiment is consideredagain. In the first embodiment, the reception is failed with respect tothe frame sets 1, 2, and 3 corresponding to the sequence numbers 101,102, and 103, and the subheader SH4 in the frame set 4 corresponding tothe sequence number 104 is determined to be not erroneous (i.e.,correct). However, the error is detected by the FCS field associatedwith FB field FB4, and therefore the acknowledgement frame is notgenerated and transmitted. However, in the eleventh embodiment, becausethe SH field SH4 can be correctly extracted, the acknowledgement frameis generated and transmitted. The method for setting the sequence numberwhich the acknowledgement frame indicates is the same with that of thefirst to tenth embodiments. That is, the successively and successfullyreceived maximum sequence number is not updated by receiving the dataframe. If the data frames up to the sequence number 100 are successfullyreceived before the reception of the data frame of FIG. 6, the sequencenumber 100 is retained as the maximum sequence number. In such case, theacknowledgement frame in which the sequence number 100 is set istransmitted in response to the data frame of FIG. 6.

The wireless communication terminal that transmitted the data framerecognizes it is necessary to retransmit the data items from thesequence number 101. And further by the fact that the acknowledgement isreceived from the wireless communication terminal of the destination,the wireless communication terminal can recognize that some of the dataitems successfully reached the wireless communication terminal of thedestination, namely, the connection state is maintained, and that thewireless communication terminal of the destination is currently in areceivable state even if the wireless communication terminal of thedestination performs a power-saving operation. This serves as asubstitute for transmitting a probe frame to confirm the connection withthe other wireless communication terminal of the communication pair orconfirm whether the other wireless communication terminal of thecommunication pair is in a receivable state.

Twelfth Embodiment

A twelfth embodiment can be applied to the first to eleventhembodiments. The twelfth embodiment relates to the operations in thewireless communication terminal on the data transmission side and thewireless communication terminal on the data reception side when noresponse to the initial data frame is received after the connection isestablished.

In the initial data frame after the connection is established, on thebasis of the second embodiment, the bit (SYNC) indicating the start ofthe sequence number is set in the SH field of the frame set in which theinitial sequence number is set. The wireless communication terminal onthe data reception side correctly receives the SH field in which the bitindicating the start of the sequence number is set and transmits theacknowledgement frame when the response condition is satisfied. At thispoint, the corresponding bit (SYNC) is also set in the SH field of theacknowledgement frame.

The case in which the wireless communication terminal on the datatransmission side cannot correctly receive the acknowledgement frame inwhich the bit is set is described in the twelfth embodiment.

The case will be described with reference to FIG. 24. In FIG. 24,assuming that the sequence number is started from the sequence number253 (starting point of sliding window Win_s=253), the frame set to whichthe sequence number 253 is allocated is located first in the data frame,and the bit indicating the start of the sequence number is set in theframe set (SYNC=1 and SN=253). Other three frame sets are aggregated inthe same data frame. The three frame sets have the sequence numbers 254,255, and 0, respectively. It is assumed that the maximum number of acounter for the sequence numbers is 255, and it is assumed that thecounter returns to 0 when reaching the maximum number 255. When all theframe sets of the data frame are correctly received, the acknowledgementframe showing that the successively and successfully received maximumsequence number is 0 and that the notification of the start of thesequence number is received (SYNC=1 and SN=0) is transmitted because thesuccessively and successfully received maximum sequence number becomes 0in the wireless communication terminal on the data reception side. Here,it is assumed that the acknowledgement frame is not correctly receivedby the wireless communication terminal on the data transmission side. Atthis point, the wireless communication terminal on the data transmissionside does not change the sliding window on the data transmission side(Win_s=253). The wireless communication terminal on the datatransmission side waits for the acknowledgement frame for apredetermined time after transmitting the initial data frame. Thewireless communication terminal on the data transmission sideretransmits the data frame with the predetermined IFS when determiningthat the acknowledgement frame is not received after a predeterminedtime elapses. In the twelfth embodiment, as illustrated in FIG. 24, thetransmission is performed while the frame sets from the sequence number253 are set in the data frame. Because the wireless communicationterminal on the data transmission side cannot confirm that the wirelesscommunication terminal on the data reception side received thenotification of the start of the sequence number by the acknowledgementframe, the bit indicating the start of the sequence number is set againin the frame set having the sequence number 253 (SYNC=1 and SN=253). Thewireless communication terminal on the data reception side that receivesthe retransmitted data frame transmits the acknowledgement frame tocontinue the data frame exchange as described previously. On the otherhand, the wireless communication terminal on the data reception sidestarts the error process when receiving data frames illustrated belowthe downward arrow in FIG. 24. When the starting sequence number isdifferent from the former one (SYNC=1 and SN=254) as illustrated by thefirst data frame below the downward arrow, or when the bit indicatingthe start of the sequence number is not set as illustrated by the seconddata frame below the downward arrow (SYNC=0 and SN=253), the wirelesscommunication terminal on the data reception side starts the errorprocess.

A processing method in which the wireless communication terminal on thedata reception side determines that the two data frames below thedownward arrow are erroneous while the retransmitted data frame in theupper portion of FIG. 24 is correct will specifically be describedbelow.

For example, in the wireless communication terminal, two parametersSync1 and StartSN are prepared to perform the determination process. Atleast Sync1 is set to 0 immediately after the connection is established.

When the wireless communication terminal receives the initial data framefrom the other wireless communication terminal of communication pairafter the connection is established (that is, when Sync1 is 0: condition1), the bit indicating the start of the sequence number is set in thefirst frame set of the data frame, and the bit indicating the start ofthe sequence number is not set in the correct SH fields of all the otherframe sets (condition 2). At this point, the wireless communicationterminal determines that the use of the bit indicating the start of thesequence number is correct. The SN field (sequence number) of the SHfield in which the bit indicating the start of the sequence number isset is written in StartSN, and Sync1 is incremented by 1 (that is, Sync1becomes 1). This is the process performed in receiving the initial dataframe in FIG. 24. When condition 2 is not satisfied, the error processis started because the use of the bit indicating the start of thesequence number is not correct.

When the wireless communication terminal receives once a data frame inwhich the use of the bit indicating the start of the sequence number iscorrect after the connection is established (that is, when Sync1 is 1:condition 3), the wireless communication terminal determines whether acondition 4 is satisfied. The condition 4 is that, the bit indicatingthe start of the sequence number is set in the first frame set of thesubsequently received data frame, and the bit indicating the start ofthe sequence number is not set in the correct SH fields of all the otherframe sets. When condition 4 is satisfied, the wireless communicationterminal determines whether the SN field (sequence number) of the SHfield in which the bit indicating the start of the sequence number isequal to the retained StartSN (condition 5). When the SN field (sequencenumber) is equal to the retained StartSN, the wireless communicationterminal determines that the use of the bit indicating the start of thesequence number is correct. Sync1 is maintained (that is, Sync1 is 1).This is the process performed in receiving the correct retransmitteddata frame in FIG. 24. On the other hand, when condition 5 is notsatisfied, the error process is started because the use of the bitindicating the start of the sequence number is not correct. This is theprocess performed in receiving the first data frame below the downwardarrow in FIG. 24. When condition 4 is not satisfied, the wirelesscommunication terminal determines whether the bit indicating the startof the sequence number is not set in the frame sets of all the correctSH fields included in the received data frame (condition 6). Whencondition 6 is satisfied, the wireless communication terminal determineswhether the minimum sequence number included in the received data frameis larger than StartSN (condition 7). When condition 7 is satisfied, thewireless communication terminal determines that the use of the bitindicating the start of the sequence number is correct. Sync1 isincremented by 1 (that is, Sync1 becomes 2). This is the processperformed in the case, in which the wireless communication terminalcorrectly receives an acknowledgement frame to the initial data frameafter the connection is established and the sliding window on the datatransmission side is updated to transmit a next data frame. Whencondition 7 is not satisfied, the error process is started because theuse of the bit indicating the start of the sequence number is notcorrect. This is the process performed in receiving the second dataframe below the downward arrow in FIG. 24. When condition 6 is notsatisfied, the error process is started because the use of the bitindicating the start of the sequence number is not correct.

In receiving the next data frame after the wireless communicationterminal correctly receives the acknowledgement frame to the initialdata frame following the connection establishment and the sliding windowon the data transmission side is updated to transmit a next data frame(that is, when Sync1 is 2, and when neither condition 1 nor condition 2is satisfied), the wireless communication terminal determines that theuse of the bit indicating the start of the sequence number is correct,when the bit indicating the start of the sequence number is not set inthe frame sets of all the correct SH fields included in the receiveddata frame (condition 8). Sync1 is maintained (that is, Sync1 is 2).When condition 8 is not satisfied, the error process is started becausethe use of the bit indicating the start of the sequence number is notcorrect.

FIG. 25 illustrates an example in which a processing operation todetermine whether the bit indicating the start of the sequence number iscorrectly used is expressed in C-like language.

Thus, after the connection is established, because the initial dataframe has a role in making the indication of the start of the sequencenumber, it is necessary to securely transmit the initial data frame tothe wireless communication terminal on the data reception side.Desirably the robust modulation and coding scheme is selected, moredesirably the most robust modulation and coding scheme is selected.

Therefore, the wireless communication terminal on the data receptionside can securely receive indication of the start of the sequencenumber. Therefore, the operation can be demonstrated when the wirelesscommunication terminal on the data transmission side cannot correctlyreceive the acknowledgement frame which is a response to the data frameand includes the indication of the start of the sequence number, and theproblem that the mutual connection cannot be established due todifferent implementation can be avoided.

In the first to twelfth embodiments, the wireless communication terminalon the data transmission side and the wireless communication terminal onthe data reception side are described while distinguished from eachother. However, this relationship is not unique, and data may mutuallybe transmitted between two wireless communication terminals. At thispoint, when a data flow on one side is viewed, one of the wirelesscommunication terminals becomes the data transmission side while theother wireless communication terminal becomes the data reception side.However, the relationship is changed when the data flow on the otherside is viewed.

Thirteenth Embodiment

A wireless communication terminal according to a thirteenth embodimentincludes a buffer in addition to the configuration of the wirelesscommunication device unit of the wireless communication terminal of FIG.3. The wireless communication device of the thirteenth embodiment isconfigured to include the buffer, which allows the transmitted andreceived frames to be retained in the buffer to easily perform theretransmission process and external output process.

Fourteenth Embodiment

A wireless communication terminal according to a fourteenth embodimentincludes a bus, a processor, and an external interface in addition tothe configuration of the wireless communication terminal of thethirteenth embodiment. The processor and the external interface areconnected to the buffer through the bus. In the processor, firmware isoperated. The wireless communication device of the fourteenth embodimentis configured to include the firmware, which allows a function of thewireless communication device to be easily changed.

Fifteenth Embodiment

A wireless communication terminal according to a fifteenth embodimentincludes a clock generator in addition to the configuration of thewireless communication device unit of the wireless communicationterminal of FIG. 3. The clock generator generates a clock and outputsthe clock from an output terminal to the outside of the wirelesscommunication device. The clock generated in the wireless communicationdevice is externally output, and a host side is operated by theexternally output clock, which allows the host side and the wirelesscommunication device side to operate in synchronization with each other.

Sixteenth Embodiment

A wireless communication terminal according to a sixteenth embodimentincludes a power supply, a power supply controller, and a wireless powerfeeder in addition to the configuration of the wireless communicationdevice unit of the wireless communication terminal of FIG. 3. The powersupply controller is connected to the power supply and the wirelesspower feeder to control selection of an electric source supplied to thewireless communication device. The wireless communication device of thesixteenth embodiment is configured to include the power supply, whichallows the low-power-consumption operation in which the power supply iscontrolled.

Seventeenth Embodiment

A wireless communication terminal according to a seventeenth embodimentincludes an SIM card in addition to the configuration of the wirelesscommunication terminal of the sixteenth embodiment. The SIM card isconnected to the upper layer processor 0 or the reception processor 10and the transmission processor 20. The wireless communication device ofthe seventeenth embodiment is configured to include the SIM card, whichallows authentication process to be easily performed.

Eighteenth Embodiment

A wireless communication terminal according to an eighteenth embodimentincludes a moving image compression/decompression unit in addition tothe configuration of the wireless communication terminal of thefourteenth embodiment. The moving image compression/decompression unitis connected to the bus. The wireless communication device of theeighteenth embodiment is configured to include the moving imagecompression/decompression unit. Therefore, the compressed moving imagecan easily be transmitted and the received compressed moving image caneasily be decompressed.

Nineteenth Embodiment

A wireless communication terminal according to a nineteenth embodimentincludes an LED unit in addition to the configuration of the wirelesscommunication device unit of the wireless communication terminal of FIG.3. The LED unit is connected to the reception processor 10 or thetransmission processor 20 or the PHY processor 40. The wirelesscommunication device of the nineteenth embodiment is configured toinclude the LED unit, which allows the user to easily obtain indicationof the operating state of the wireless communication device.

Twentieth Embodiment

A wireless communication terminal according to a twentieth embodimentincludes a vibrator in addition to the configuration of the wirelesscommunication device unit of the wireless communication terminal of FIG.3. The vibrator is connected to at least the reception processor 10 andthe PHY processor 40. The wireless communication device of the twentiethembodiment is configured to include the vibrator, which allows the userto easily obtain indication of the operating state of the wirelesscommunication device.

Twenty-First Embodiment

In a wireless communication terminal according to a twenty-firstembodiment, as described in the first embodiment, the plurality ofdifferent PHY processors 40 are provided in addition to theconfiguration of the wireless communication device unit of the wirelesscommunication terminal of FIG. 3. The wireless communication terminal ofthe twenty-first embodiment also includes a wireless switch. Thewireless switch is connected to the plurality of different PHYprocessors 40 to switch communication among the different PHY processors40. The wireless communication device of the twenty-first embodiment isconfigured to include the plurality of different PHY processors 40, sothat the communication can be switched such that the proper PHYprocessor 40 is used depending on the situation.

Twenty-Second Embodiment

In a wireless communication terminal according to a twenty-secondembodiment, as described in the first embodiment, the plurality ofdifferent PHY processors 40 are provided in addition to theconfiguration of the wireless communication device unit of the wirelesscommunication terminal of FIG. 3. A set of the reception processor 10,the transmission processor 20, and the access controller 30, whichcorrespond to each PHY processor 40, is provided in the wirelesscommunication terminal of the twenty-second embodiment. The wirelesscommunication terminal of the twenty-second embodiment also includes awireless switch. The wireless switch is connected so as to switchcommunication among the sets of the reception processors 10, thetransmission processors 20, and the access controllers 30, and thewireless switch switches among a plurality of communication methods ofthe different sets of the reception processors 10, the transmissionprocessors 20, the access controllers 30, and the PHY processors 40. Thewireless communication device of the twenty-second embodiment isconfigured to include the plurality of different sets of the receptionprocessors 10, the transmission processors 20, the access controllers30, and the PHY processors 40, so that the communication can be switchedsuch that the proper set of the reception processor 10, the transmissionprocessor 20, the access controller 30, and the PHY processor 40 is useddepending on the situation.

Twenty-Third Embodiment

A wireless communication terminal according to a twenty-third embodimentincludes a switch (SW) in addition to the configuration of the wirelesscommunication terminal of the twenty-first embodiment. The switch isconnected to the antenna 60, the plurality of different PHY processors40, and wireless switch. The wireless communication device of thetwenty-third embodiment is configured to include the switch, so that thecommunication in which the proper PHY processor 40 is used can beswitched depending on the situation while the antenna is shared.

Twenty-Fourth Embodiment

A wireless communication terminal according to a twenty-fourthembodiment includes a switch (SW) in addition to the configuration ofthe wireless communication terminal of the twenty-second embodiment. Theswitch is connected to the antenna 60, a base of the set of thereception processors 10, the transmission processors 20, and the accesscontrollers 30, and the wireless switch. The wireless communicationdevice of the twenty-fourth embodiment is configured to include theswitch, so that the communication can be switched such that the properset of the reception processor 10, the transmission processor 20, theaccess controller 30, and the PHY processor 40 is used depending on thesituation.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1. (canceled)
 2. A wireless communication terminal comprising: atransmitter which transmits a physical packet including one or moreframe sets including a subheader field, a frame body field, and a framecheck sequence field; a receiver which receives a response framenotifying a successively and successfully received maximum sequencenumber; and a retransmission controller which controls retransmissiondata in the frame body field, wherein the subheader field includes: asequence number field which notifies a sequence number corresponding tothe frame body field; a bit indicating a sequence number start to notifywhether or not the sequence number indicated by the sequence numberfield is a sequence starting number; and a frame body length field whichnotifies a length of the frame body field; wherein the transmitter setsthe bit indicating the sequence number start of the frame set to whichan initial sequence number is set; and wherein the retransmissioncontroller controls retransmission based on (i) whether or not receivingof the response frame has begun after a fixed time has elapsed fromtransmission of the physical packet, (ii) the successively andsuccessfully received maximum sequence number notified by the responseframe, and (iii) a bit of recognition of sequence start included in theresponse frame.
 3. The wireless communication terminal according toclaim 2, further comprising an antenna for wireless communication. 4.The wireless communication terminal according to claim 2, furthercomprising a buffer which maintains the physical packet for transmissionor reception.
 5. The wireless communication terminal according to claim4, further comprising a processor which executes firmware to realize afunction of a wireless communication terminal, the processor beingconnected to the buffer via a bus.
 6. The wireless communicationterminal according to claim 2, further comprising a clock generatorwhich generates a clock to operate a host-side device and a wirelesscommunication terminal in synchronization with each other.
 7. Thewireless communication terminal according to claim 2, furthercomprising: a power supply; a wireless power feeder; and a power supplycontroller which controls selection of a power source supplied to thewireless communication terminal, the power controller being connected tothe power supply and the wireless power feeder.
 8. The wirelesscommunication terminal according to claim 2, further comprising a SIMcard to perform an authentication process.
 9. The wireless communicationterminal according to claim 5, further comprising a moving imagecompression/decompression unit which compresses and decompresses amoving image, the moving image compression/decompression unit beingconnected to the bus.
 10. The wireless communication terminal accordingto claim 2, further comprising an LED unit to notify a user of anoperating state of the wireless communication terminal.
 11. The wirelesscommunication terminal according to claim 2, further comprising avibrator unit to notify a user of an operating state of the wirelesscommunication terminal.
 12. The wireless communication terminalaccording to claim 2, further comprising: a first PHY processor toprocess the physical packet for communication; a second PHY processor toprocess the physical packet for communication; and a communicationswitch to switch between a communication by the first PHY processor anda communication by the second PHY processor.
 13. The wirelesscommunication terminal according to claim 12, wherein a plurality of thetransmitters and the receivers are provided such that the first PHYprocessor and the second PHY processor each have a respectivetransmitter and receiver.
 14. The wireless communication terminalaccording to claim 12, further comprising a switch to connect theantenna to one of the first PHY processor and the second PHY processor.15. The wireless communication terminal according to claim 13, furthercomprising a switch to connect the antenna to one of (i) the first PHYprocessor and the transmitter and the receiver corresponding to thefirst PHY processor, and (ii) the second PHY processor and thetransmitter and the receiver corresponding to the second PHY processor.16. A wireless communication terminal comprising: a receiver whichreceives a physical packet including one or more frame sets including asubheader field, a frame body field, and a frame check sequence field; afirst processor which extracts a correct frame body field using a framebody length field notifying the frame body field included in thesubheader field, and the frame check sequence field; a first storageunit which stores the frame body field extracted by the first processor,and a sequence number field corresponding to the frame body field; asecond storage unit which stores a successively and successfullyreceived maximum sequence number, the successively and successfullyreceived maximum sequence number being updated based on a result of thefirst processor; a second processor which relays, to receptionprocessing that continues from the first storage unit, a frame bodyfield corresponding to a sequence number up to the successively andsuccessfully received maximum sequence number stored in the secondstorage unit; and a transmitter which obtains the successively andsuccessfully received maximum sequence number stored in the secondstorage unit upon reception of an instruction to transmit a responseframe, the instruction being received from the second processor, and thetransmitter transmitting a response frame which notifies the sequencenumber, wherein the second storage unit updates the successively andsuccessfully received maximum sequence number based on one of (i) aresult of processing of the first processor and (ii) information storedat the first storage unit.
 17. The wireless communication terminalaccording to claim 16, further comprising a detector which detects aviolation of continuity of sequence numbers based on a sequence numberincluded in the physical packet and a buffer size of the first storageunit.
 18. The wireless communication terminal according to claim 16,wherein the subheader field includes a bit which indicating a sequencenumber start to notify whether or not a value indicated by the sequencenumber field is a sequence starting number.
 19. The wirelesscommunication terminal according to claim 18, further comprising: aparameter storage unit which stores a first parameter related toreception of the bit indicating the sequence number start, and a secondparameter representing a sequence number corresponding to the bitindicating the sequence number start; and a determination unit whichdetermines whether or not usage of the bit indicating the sequencenumber start is correct by checking the subheader in the physical packetreceived by the receiver based on the first and second parameters. 20.The wireless communication terminal according to claim 16, furthercomprising an antenna for wireless communication.
 21. The wirelesscommunication terminal according to claim 16, further comprising abuffer which maintains the physical packet for transmission orreception.
 22. The wireless communication terminal according to claim21, further comprising a processor which executes firmware to realize afunction of a wireless communication terminal, the processor beingconnected to the buffer via a bus.
 23. The wireless communicationterminal according to claim 16, further comprising a clock generatorwhich generates a clock to operate a host-side device and a wirelesscommunication terminal in synchronization with each other.
 24. Thewireless communication terminal according to claim 16, furthercomprising: a power supply; a wireless power feeder; and a power supplycontroller which controls selection of a power source supplied to thewireless communication terminal, the power controller being connected tothe power supply and the wireless power feeder.
 25. The wirelesscommunication terminal according to claim 16, further comprising a SIMcard to perform an authentication process.
 26. The wirelesscommunication terminal according to claim 22, further comprising amoving image compression/decompression unit which compresses anddecompresses a moving image, the moving image compression/decompressionunit being connected to the bus.
 27. The wireless communication terminalaccording to claim 16, further comprising an LED unit to notify a userof an operating state of the wireless communication terminal.
 28. Thewireless communication terminal according to claim 16, furthercomprising a vibrator unit to notify a user of an operating state of thewireless communication terminal.
 29. The wireless communication terminalaccording to claim 16, further comprising: a first PHY processor toprocess the physical packet for communication; a second PHY processor toprocess the physical packet for communication; and a communicationswitch to switch between a communication by the first PHY processor anda communication by the second PHY processor.
 30. The wirelesscommunication terminal according to claim 29, wherein a plurality of thetransmitters and the receivers are provided such that the first PHYprocessor and the second PHY processor each have a respectivetransmitter and receiver.
 31. The wireless communication terminalaccording to claim 29, further comprising a switch to connect theantenna to one of the first PHY processor and the second PHY processor.32. The wireless communication terminal according to claim 30, furthercomprising a switch to connect the antenna to one of (i) the first PHYprocessor and the transmitter and the receiver corresponding to thefirst PHY processor, and (ii) the second PHY processor and thetransmitter and the receiver corresponding to the second PHY processor.